Imaging system, method for processing thereof and program

ABSTRACT

An imaging apparatus is provided, which improves correction accuracy at the time of pixel addition reading and scarcely deteriorates in resolution of the image data. This apparatus comprises: a conversion unit comprising a plurality of unit-pixels and converting an incident radiation or a light into pixel information; a signal processing unit capable of reading the pixel information for each unit-pixel, or capable of reading additional added pixel information for a plurality of unit-pixels, based on a control from a control unit for controlling a driving of the conversion unit according to a plurality of operation modes; a storage unit for storing a plurality of correction informations according to the plurality of operating modes; and a correction unit for performing the correction of the pixel information based on the correction information extracted from the plurality of correct informations according to the operation mode.

TECHNICAL FIELD

The present invention relates to an imaging system applied to a medicaldiagnostic imaging apparatus, non-destructive inspection apparatus,analytical instrument using radiation, method for processing thereof,and program allowing a computer to execute the method for processing. Inparticular, the invention relates to the imaging system intending toimprove sensitivity and frame rate by pixel-addition and at the sametime comprising defect compensating functions. Incidentally, in thepresent specification, radiation also includes an electromagnetic wavesuch as a visible light, and an x-ray, α-ray, β-ray, and γ-ray.

BACKGROUND ART

Heretofore, as the still image photography of an x-ray in medicaltreatment, the main stream has been a film system in which an x-ray isirradiated on a patient, and its transmitted x-ray image is exposed on afilm. The film has functions of displaying and recording information,and can be enlarged to a large area, and is high in gradation, and yet,it is light in weight and can be easily handled. Therefore, it ispopularized throughout the world. On the other hand, left behind to besolved are complications requiring development processing, the problemof a location for storing over a long period of time, and the problem ofmanpower and time required for retrieval.

In the meantime, as a moving image radiography, the main stream has beenan image intensifier (hereinafter, abbreviated as [I.I.]). Since theI.I. uses photo-multiplying effect inside the apparatus, in general,sensitivity is high, and it is excellent in view of a low dosage ofexposure to radiation. On the other hand, shortcomings such as adistortion of the peripheral image due to optical influences, lowcontrast, and large size of the apparatus are pointed out. The I.I. hasnot only the transmitted image of the patient monitored by a doctor, butalso can convert an analogue output of CCD into a digital signal so asto record, display or store the same. However, since a high gradation isrequired for diagnosis, even if the I.I. is used for the transmittedimage, there are often the cases where the film is used in the stillimage photography.

In recent years, a demand for digitalization of the x-ray image has beenincreasing in the hospitals, and in place of the film, an imaging devicedisposed in a two-dimensional array pattern with a solid state imagesensing device converting an electromagnetic wave such as a visiblelight and radiation into an electrical signal began to be used. Thisimaging device is called a FPD (Flat Panel Detector) for short.

Since this FPD can substitute an x-ray image with digital information,the image information can be transferred far away and instantaneously.Hence, an advantage is also offered in that, while being far away, anadvanced diagnosis equal to a centrally located university hospital canbe received. If the film is not used, an advantage is also offered inthat a storage space for the film in the hospital can be eliminated. Inthe future, if an excellent image data processing technique can beintroduced, a potential for an automatic diagnosis by using a computerwithout intermediary of a radiologist is greatly anticipated.

Further, a radiation imaging apparatus capable of radiographing a stillimage by using an amorphous silicon thin film semiconductor for thesolid state image sensing device has been put to a practical use. As forthis radiation imaging apparatus, a large area electronic displayexceeding 40 cm square covering the size of a chest region of the humanbody is realized by using the manufacturing technique of the amorphoussilicon thin film semiconductor. Since this manufacturing processing isrelatively easy, in the future, realization of an inexpensive radiationimaging apparatus is anticipated. Moreover, since amorphous silicon canbe made into a thin glass of not more than 1 mm, an advantage is offeredin that a thickness as a detector can be made extremely thin.

Such radiation imaging apparatus is disclosed, for example, in JapanesePatent Application Laid-Open No. H08-116044. Further, in recent years,the radiographing of a moving image by such radiation imaging apparatusis being developed. If one set of such apparatus can be manufactured ata low cost, the still and moving images can be imaged, and therefore, itwill be expected to become popular at the great many numbers ofhospitals.

When the moving image is imaged by using such radiation imagingapparatus, a problem to be solved is that, as compared with the stillimage, a reading time is made shorter (frame rate is made faster) andS/N is improved. Hence, when the moving image is radiographed, a drivingwhich is generally called as “pixel-addition” is sometimes performed.Usually, as against reading a single pixel as one pixel (hereinafter,this one pixel is referred to as “unit-pixel”), in the case of thepixel-addition, a plurality of pixels is put together and read as onepixel (hereinafter, this one pixel is referred to as “multi-pixel”).Hence, for example, when two pixels are bound, though the signal isdoubled, the noise becomes only (√2) times, and therefore, as the S/N,as a S/N of 2/(√2)=(√2)≈1.4 times can be obtained.

Further, the pixel-addition includes a digital-addition and ananalogue-addition. The digital-addition is read as usual and performs anA/D conversion, and after that, digitally binds up the unit-pixel andconstitutes the multi-pixel. In contrast to this, the analogue-additionis a technique, in which analogue signals are bound up before A/Dconversion, and after that, the A/D conversion is performed. Thedigital-addition is read as usual, and then, performs the A/Dconversion, and therefore, though the reading time is not different fromthe case where the pixel-addition is not performed (hereinafter,referred to as “pixel non-addition”, the analogue-addition can shortenthe reading time.

Further, as for a driving method for addition and reading the unit-pixelin a signal wiring direction, for example, it is disclosed in“Proceeding of SPIE, Vol. 5368, Item 721, 2004, Eric Beuville, IndigoSystem Corporation”. In this Non-Patent Document, the pixel-addition(averaging out of odd number lines and even number lines) in a signalwiring direction by a sampling and holding circuit unit at the precedingstage of an AD converter (ADC) is performed. The signal is averaged out,and the noise is increased by 1/(√2) times so that S/N=(√2) times. Thus,in the moving image radiographing, the driving by the pixel-addition canbe said to be an important method for driving.

Further, though the radiation imaging apparatus performs various imageprocessings for the radiographed image, the basic image processing amongthem includes an offset correction and gain correction, and adefect-correction. The offset correction is a processing for correctinga dark component of a photoelectrical conversion element and an offsetcomponent of a signal processing circuit unit. On the other hand, thegain correction is a processing for correcting the fluctuation insensitivity of the photoelectric conversion element and the gainfluctuation in the signal processing circuit unit. This gain correctionis performed such that, usually before radiographing an object, an x-rayis irradiated in a state in which no object exists, thereby performingradiographing, and by using the radiographed image as an image for gaincorrection, a division processing is performed for the image in whichthe object is radiographed, so that the correction is performed.

Further, the defect correction is a processing for correcting the pixelvalue of a defective pixel by using the pixel value of the defectivepixel periphery. Although such radiation imaging apparatus comprises asemiconductor, when manufacturing the apparatus, due to a defect causedin the semiconductor and an influence of the dust adhered in themanufacturing process, there are often the cases where a defect iscaused in the pixel. T₀ manufacture the whole of a great many number ofpixels comprising the radiation imaging apparatus without causing anydefect is extremely difficult. Consequently, if the imaging apparatusincluding the defective pixel is not used, this will invite a reductionin yield ratio of the imaging apparatus. However, if the imagingapparatus including the defective pixel is used as it is, the quality ofthe image obtained by the radiographing is remarkably deteriorated dueto the influence of the defective pixel.

Hence, in order to use the imaging apparatus including the defectivepixel, heretofore, a correction technique for the defect pixel has beenproposed. For example, the technique disclosed in Japanese PatentPublication No. H05-023551 corrects the defect by using an average rateof the pixel value in the periphery of the defective pixel.

DISCLOSURE OF THE INVENTION

However, particularly with respect to the gain correction and the defectcorrection, when such pixel-addition reading is performed, even when thecorrection used in case of performing the pixel non-addition reading isperformed as it is, there has been a problem in that the correction isnot effectively performed.

The present invention has been carried out in view of the abovedescribed problem, and aims at providing an imaging apparatus, methodfor processing, and program, which improve correction accuracy at thetime of pixel-addition reading and scarcely deteriorates in resolutionof image data.

The imaging apparatus of the present invention comprises:

a conversion unit comprising a plurality of unit-pixels and convertingan incident radiation or light into pixel information; a signalprocessing unit capable of reading pixel information for eachunit-pixel, or capable of reading an added pixel information foraddition plurality of unit-pixels, based on a control from a controlunit for controlling a driving of the conversion unit according to aplurality of operation modes; a storage unit for storing a plurality ofcorrection informations according to a plurality of operation modes; anda correction unit for performing a correction of the pixel informationbased on the correction information extracted from the plurality ofcorrection informations according to the operation mode.

Further, in the imaging apparatus of the present invention, the storageunit comprises unit-pixel defect information which is defect informationregarding the unit-pixel and the multi-pixel defect information which isdefect information regarding the multi-pixel. The correction unitperforms correction based on the unit-pixel defect information for thepixel information which is converted in the conversion unit according tothe plurality of operation modes and read for each unit-pixel in thesignal processing unit or performs correction based on the multi-pixeldefect information for the pixel information which is converted in theconversion unit and read for each multi-pixel in the signal processingunit.

Further, in the imaging apparatus of the present invention, the storageunit comprises correction information for a plurality of gaincorrections which are converted in the conversion unit in a state inwhich no object exists and read by the signal processing unit for eachplurality of operation modes, and the correction unit extracts thecorrection information for the corresponding gain correction from thestorage unit according to the plurality of operation modes, and performsthe gain correction of an object image based on the pixel information byusing the correction information for the gain correction.

The method for processing of the imaging apparatus of the presentinvention is a method for processing of the imaging apparatuscomprising: a conversion unit comprising a plurality of unit-pixels andconverting an incident radiation or light into pixel information; asignal processing unit capable of reading the pixel information for eachunit-pixel, or capable of reading the pixel information for addition aplurality of unit-pixels, based on a control from a control unit forcontrolling a driving of the conversion unit according to a plurality ofoperation modes; a storage unit for storing a plurality of correctioninformations according to the plurality of operating modes; and acorrection unit for performing the correction of the pixel informationsbased on the correction information extracted from the plurality ofcorrection information according to the operation mode, wherein themethod for processing comprises a step of reading the pixel informationfor each unit-pixel in the conversion unit based on a control from thecontrol unit or reading the pixel information on multi-pixel by additiona plurality of unit-pixels, a step of storing the unit-pixel defectinformation which is defect information regarding the unit-pixel, and astep of storing the multi-pixel defect information which is defectinformation regarding the multi-pixel.

Further, the method for processing of the imaging apparatus of thepresent invention is a method for processing of the imaging apparatuscomprising: conversion unit comprising a plurality of unit-pixels andconverting an incident radiation or light into pixel information; asignal processing unit capable of reading the pixel information for eachunit-pixel, or capable of reading an added pixel information foraddition a plurality of unit-pixels, based on a control from a controlunit for controlling a driving of the conversion unit according to aplurality of operation modes; a storage unit for storing a plurality ofcorrection informations according to the plurality of operating modes;and a correction unit for performing the correction of the pixelinformations based on the correction information extracted from theplurality of correction information according to the operation mode,wherein the method for processing comprises a storing step of storing inthe storing unit a plurality of correction information converted in theconversion unit in a state in which no object exists for each pluralityof operation modes and read by the signal processing unit; an extractingstep of extracting the corresponding correction information from thestorage unit based on an operation mode set by the operation modesetting unit; and an image processing step of performing gain correctionof the object image based on the pixel information converted in theconversion unit by using the correction information extracted by theextracting step.

The readable storage medium for storing a program of the presentinvention is a readable storage medium for storing a program allowing acomputer to execute the method for processing of the imaging apparatuscomprising: a conversion unit comprising a plurality of unit-pixels andconverting an incident radiation or light into pixel information; asignal processing unit capable of reading the pixel information for eachunit-pixel, or capable of reading an added pixel information foraddition a plurality of unit-pixels, based on a control from a controlunit for controlling a driving of the conversion unit according to aplurality of operation modes; a storage unit for storing a plurality ofcorrection informations according to the plurality of operating modes;and a correction unit for performing the correction of the pixelinformation based on the correction information extracted from theplurality of correct information according to the operation mode,wherein the program allows a computer to execute a reading step ofreading the pixel information for each pixel unit in the conversion unitbased on a control from the control unit or reading the pixelinformation on the multi-pixel by addition the plurality of unit-pixels,a unit-pixel defect information storing step of storing the unit-pixeldefect information which is the defect information regarding theunit-pixel, and a multi-pixel defect information storing step of storingthe multi-pixel defect information which is the defect informationregarding the multi-pixel.

Further, the readable storage medium for storing a program of thepresent invention is a readable storage medium for storing a programallowing a computer to execute the method for processing of the imagingapparatus, comprising: conversion unit comprising a plurality ofunit-pixels and converting an incident radiation or light into pixelinformation; a signal processing unit capable of reading the pixelinformation for each unit-pixel, or capable of reading an added pixelinformation for addition a plurality of unit-pixels, based on a controlfrom a control unit for controlling a driving of the conversion unitaccording to a plurality of operation modes; a storage unit for storinga plurality of correction informations according to the plurality ofoperating modes; and a correction unit for performing the correction ofthe pixel information based on the correction information extracted fromthe plurality of correct information according to the operation mode,and wherein the program allows a computer to execute a storing step ofstoring in the storing unit a plurality of correction informationconverted in the conversion unit in a state in which no object existsfor each plurality of operation modes and read by the signal processingmeans, wherein the program allows a computer to execute: s storing stepof storing in the storage unit a plurality of pieces of correctioninformation converted in the conversion unit in a state in which noobject exists and read by the signal processing means; an extractingstep of extracting the corresponding correction information from thestorage unit based on an operation mode set by the operation modesetting means, and an image processing step of performing gaincorrection of the object image based on the pixel information convertedin the conversion unit by using the correction information extracted bythe extracting step.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a radiation imaging systemaccording to a first embodiment.

FIG. 2 is an equivalent circuit diagram illustrating a detailedconfiguration of a radiation imaging apparatus.

FIG. 3 is a timing chart illustrating a first method for driving(unit-pixel reading mode) the radiation imaging apparatus.

FIG. 4 is a timing chart illustrating a second method for driving(four-pixel-addition reading mode) the radiation imaging apparatus.

FIG. 5 is a timing chart illustrating a third method for driving(nine-pixel-addition reading mode) the radiation imaging apparatus.

FIG. 6 is a flowchart illustrating a production process of a defectcoordinate table used for a unit-pixel reading mode of FIG. 3.

FIG. 7 is a flowchart illustrating the production process of the defectcoordinate table used for a four-pixel-addition reading mode of FIG. 4.

FIG. 8 is a flowchart illustrating the production process of the defectcoordinate table used for a nine-pixel-addition reading mode of FIG. 5.

FIGS. 9A and 9B are views illustrating a defective unit-pixel when theradiation imaging apparatus of FIG. 2 is read by an unit-pixel readingmode and one example of a unit-pixel defect coordinate table.

FIGS. 10A and 10B are views illustrating defective multi-pixel when theradiation imaging apparatus of FIG. 2 is read by the four-pixel-additionreading mode and one example of a defect coordinate table of multi-pixelby the four-pixel-addition.

FIGS. 11A and 11B are views illustrating defective multi-pixel when theradiation imaging apparatus of FIG. 2 is read by the nine-pixel-additionmode and one example of the multi-pixel defect coordinate table by thenine-pixel-addition.

FIG. 12 is a flowchart illustrating the correction processing of thedefective pixel in the radiation imaging system according to the firstembodiment.

FIG. 13 is a flowchart illustrating a method for extracting thedefective pixel in the radiation imaging system according to a secondembodiment.

FIGS. 14A and 14B are views illustrating an output value in eachunit-pixel and one example of the unit-pixel defect coordinate table.

FIGS. 15A and 15B are views illustrating the output value of each of themulti-pixel by the four-pixel-addition and one example of themulti-pixel defect coordinate table by the four-pixel-addition.

FIGS. 16A and 16B are views illustrating the output value of each of themulti-pixel in a 16-pixel-addition and one example of the multi-pixeldefect coordinate table by the 16-pixel-addition.

FIG. 17 is a flowchart illustrating the correction processing of thedefective pixel in the radiation imaging system according to a thirdembodiment.

FIG. 18 is an equivalent value circuit diagram illustrating the detailedconfiguration in the radiation imaging apparatus of the radiationimaging system according to a fourth embodiment.

FIG. 19 is a view illustrating an operation mode of the radiationimaging system according to the fourth embodiment.

FIG. 20 is a timing chart illustrating a method for driving in a pixelnon-addition of the radiation imaging system according to the fourthembodiment.

FIG. 21 is a timing chart illustrating the method for driving in a twoby two-pixel-addition of the radiation imaging system according to thefourth embodiment.

FIG. 22 is a timing chart illustrating the method for driving in a fourby four-pixel-addition of the radiation imaging system according to thefourth embodiment.

FIGS. 23A, 23B and 23C are schematic circuit diagrams illustrating themethod for driving according to each pixel-addition mode.

FIGS. 24A and 24B are schematic circuit diagrams for describing agenerating mechanism of an artifact.

FIG. 25 is a flowchart illustrating an acquisition process of the imagefor gain correction of the radiation imaging system according to thefourth embodiment.

FIG. 26 is a flowchart illustrating a processing in the radiographingoperation of the radiation imaging system according to the fourthembodiment.

FIG. 27 is a flowchart illustrating the acquisition process of the imagefor gain correction of the radiation imaging system according to a fifthembodiment.

FIG. 28 is an equivalent value circuit diagram illustrating the detailedconfiguration in a radiation imaging apparatus 140 of the radiationimaging system according to a sixth embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

In the first to third embodiments illustrated below, a defect correctionwhen a pixel-addition is performed will be described. The problem areaof the defect correction when the pixel-addition found by the presentinventor is performed will be described below.

When pixel-addition reading is performed in the radiation imagingapparatus of the present invention, in case even one pixel of thedefective pixel is included in each unit-pixel among multi-pixel, thesemulti-pixel become defective pixels. Hence, assuming that a conventionaldefect correction technique is applied, information on the adjacentmulti-pixel are appropriated for (substituted for) these defectivemulti-pixel.

In this case, despite the fact that non-defective but effective pixelsare included as unit-pixels even among the defective multi-pixel, theeffective pixels are bound to the information on the defective pixelsand read by the pixel-addition reading, and therefore, information onthese non-defective but effective pixels becomes invalidated. Forexample, in the case of the four-pixel-addition reading, its defect is adefect of the four-pixels, and lack of information is large. In thiscase, the correction of the defective multi-pixel was performed not bythe adjacent unit-pixel closest to the defect unit-pixel but by theinformation on the adjacent multi-pixel far away. As a result, there hasbeen a problem in that the deterioration of the resolution in the imageends up becoming worse.

Hence, a first aspect of the invention of the present applicationaccording to the first, second and third embodiments has been carriedout in view of the above described problem, and aims at providing animaging system, the method for processing and program thereof capable ofreducing the defective pixel at the time of the pixel-addition readingand having a larger number of pixel information in the image data andscarcely deteriorating in the resolution of the image data.

Embodiments of the first aspect of the invention of the presentapplication will be described below.

FIRST EMBODIMENT

FIG. 1 is a schematic block diagram of a radiation imaging systemaccording to a first embodiment. As illustrated in FIG. 1, the radiationimaging system of the present embodiment comprises by being separatedinto an x-ray room 301, an x-ray control room 302, and a dispensary 303.

The operation of the radiation imaging system of the present embodimentis controlled by a system control unit 310. An operator interface (I/F)311 comprises a touch panel on a display, mouse, keyboard, joy stick,foot switch, which are suitably selected by an operator 305. By thisoperator interface (I/F) 311, a setting of each information such asradiographing conditions (still image, moving image, tube voltage, tubecurrent, irradiating time, and the like), radiographing timing, imageprocessing condition, test subject ID, and method for processing antakeout image can be performed. However, since almost all pieces ofinformation are transferred from a radiation information system (notillustrated), there is no need to input them individually. The importantoperation of the operator 305 is an operation to confirm theradiographed image. That is, determination is made as to if its angle iscorrect, if the patient is moving or if the image processing isappropriate and the like.

The system control unit 310 instructs a radiographing condition based onthe instruction from the operator 305 or the radiation informationsystem (not illustrated) to an imaging control unit 214 which presidesover an x-ray radiographing sequence, and controls the unit 214 so as totake in the image data. The imaging control unit 214, based on theinstruction from this system control unit 310, allows a radiationgenerating apparatus 120 which is a radiation source, bed 130 forradiographing, and radiation imaging apparatus 140 to be operated so asto take in the image data, thereby transferring it to an imageprocessing unit 10.

After transferring this image data, for example, the system control unit310 allows an image processing designated by the operator 305 to beperformed by the image processing unit 10, and this is displayed in adisplay unit 160. At the same time, the system control unit 310 allowsthe basic image processing such as offset correction, white correction,defect correction to be performed by the image processing unit 10, andstores the image data after the processing in an external memory device161. Further, based on the instruction by the operator 305, the systemcontrol unit 310 performs a re-radiographing processing and replydisplaying, transfer and storage of the image data to the apparatus on anetwork, display on a display unit, printing on a film, and the like.

Next, the configuration and operation of the radiation imaging system ofthe present embodiment will be described along a signal flow.

The radiation generating apparatus 120 comprises by including an x-raytube 121, x-ray aperture 123, and high voltage generating power source124. The x-ray tube 121 is driven by the high voltage generating powersource 124 controlled by the imaging control unit 214, and radiates anx-ray beam 125. An x-ray aperture 123 is driven by the imaging controlunit 214, and forms the x-ray beam 125 so as not to perform unnecessaryx-ray irradiation accompanied with a change in the radiographing region.The x-ray beam 125 is directed to a subject 126 lying down on a bed 130for radiographing having an x-ray transmittance.

The bed 130 for radiographing is driven based on a control of theimaging control unit 214. The x-ray beam 125 irradiated from theradiation generating apparatus 120 transmits the subject 126 and the bed130 for radiographing, and after that, is irradiated on the radiationimaging apparatus 140.

The radiation imaging apparatus 140 comprises by including a grid 141,converter 142, photoelectric conversion circuit unit 143, radiationexposure monitor 144, and external circuit unit 145.

The grid 141 reduces the influence of the x-ray scattering caused by itstransmission through the subject 126. This grid 141 comprises an x-raylow absorption material and an x-ray high absorption material, and forexample, it has a stripe structure by AI and Pb. The imaging controlunit 214 vibrates the grid 141 so that a moiré is not caused by therelationship of a grid ratio between the photoelectric conversioncircuit unit 143 and the grid 141 at the x-ray irradiating time.

The wavelength converter 142 includes a phosphor comprising one typeselected from Gd₂O₃, Gd₂O₂S, CaWO₄, CdWO₄, CsI, and ZnS as a mainingredient. In the wavelength converter 142, a main ingredient materialof the phosphor is excited by the incident x-ray of high energy, andoutputs fluorescent radiation of a visible region by re-addition energywhen re-addition. Its fluorescent radiation is attributed to the mainingredient material itself such as Gd₂O₃, Gd₂O₂S, CaWO₄, CdWO₄ and isattributed to a fluorescent radiation central material activated insidethe main ingredient material such as CsI:Tl and Zns:Ag. Adjacent to thiswavelength converter 142, the photoelectric conversion circuit unit 143is disposed.

The photoelectric conversion circuit unit 143 converts photons of thelight converted into wavelength by the wavelength converter 142 intoelectric signals by each pixel (unit-pixel) including each conversionelement. That is, the photoelectric conversion circuit unit 143radiographs a radiation image of the subject 126.

The x-ray exposure monitor 144 monitors x-ray transmission. The x-rayexposure monitor 144 may directly detect the x-ray by using a lightreceiving element such as crystal silicon or may detect a light from thewavelength converter 142. In the present embodiment, the visible light(light proportional to the x-ray image) transmitting the photoelectricconversion circuit unit 143 is detected by an amorphous silicon lightreceiving element of the x-ray exposure monitor 144 deposited on therear surface of the photoelectric conversion circuit unit 143, and thisinformation is transmitted to the imaging control unit 214. The imagingcontrol unit 214, based on the information from the x-ray exposuremonitor 144, drives the high voltage generating power source 124 so asto shut out or adjust the x-ray.

The external circuit unit 145 comprises by including a driving circuitunit for driving the photoelectric conversion circuit unit 143 and asignal processing circuit unit for reading a signal from each pixel ofthe photoelectric conversion circuit unit 143. This external circuitunit 145, under the control of the imaging control unit 214, drives thephotoelectric conversion circuit unit 143, and reads the signal fromeach pixel, and outputs it as an image signal (image data).

The image signal outputted from the radiation imaging apparatus 140 istransmitted to the image processing unit 10 inside the x-ray controlroom 302 from the x-ray room 301. At this transmission time, the insideof the x-ray room 301 is filled with a loud noise accompanied with thex-ray generation, and there are sometimes the cases where the imagesignal is not accurately transmitted because of the noise. Hence, noisesurability of a transmission route is required to be improved. Forexample, provision of a transmission route having an error correctionfunction and use of a transmission route by a pair twisting wire withshield and an optical fiber are desirable.

The image processing unit 10, based on the instruction from the imagingcontrol unit 214, switches over the display data. Further, the imageprocessing unit 10 performs in real time various correction processingssuch as an offset correction, white correction, and defect correction aswell as space filtering processing, and recursive processing, andmoreover, performs a gradation processing, scattered radiationcorrection processing, and various space frequency processing accordingto needs.

The image data processed by the image processing unit 10 is displayed ona display unit 160 as an image through a display adaptor 151. Further,the basic image data subjected to the correction processing only of theimage data at the same time as a real time image processing is stored inan external memory device 161. As the external memory device 161, a datastorage device filling a large capacity, high speed, and highreliability is desirable, and for example, a hard disk array such asRAID is desirable. Further, based on the instruction from the operator305, the image data stored in the external memory device 161 is storedin the other external memory device. At that time, the image data isreconfigured to meet the predetermined standard (for example, IS&C), andafter that, it is stored in the other external memory device. As theother external memory device, for example, there exist a magneto-opticaldisk 162 and hard disk inside a file server 170 on a LAN, and the like.

The radiation imaging system of the present embodiment can be alsoconnected to a LAN 171 through a LAN board 163, and is configured tohave compatibility of data with HIS. This LAN 171 is connected with amonitor 174 for displaying a moving image or still image, the fileserver 170 for filing the image data, an image printer 172 foroutputting the image to the film, image processing terminal 173 forperforming a complicated image processing and diagnostic support, andthe like. Incidentally, it goes without saying that this LAN 171 can beconnected with a plurality of radiation imaging systems. Further, theradiation imaging system in the present embodiment outputs the imagedata according to the predetermined protocol (for example, DICOM). Inaddition, the radiation imaging system can perform a real time remotediagnosis by a doctor by using the monitor 174 connected to the LAN 171at radiographing time.

Next, the detail of the radiation imaging apparatus 140 will bedescribed. FIG. 2 is an equivalent circuit diagram illustrating thedetailed configuration of the radiation imaging apparatus 140. Here, inFIG. 2, from among each component part comprising the radiation imagingapparatus 140, the photoelectric conversion circuit unit 143 and adriving circuit unit 101 provided in the external circuit unit 145 aswell as a signal processing circuit unit 102 are illustrated.

This radiation imaging apparatus 140, based on a control from theimaging control unit 214, is configured to be able to drive in variousradiographing modes including a moving image radiographing mode, a stillimage radiographing mode, the pixel reading mode in the unit-pixelreading and pixel-addition reading.

The photoelectric conversion circuit unit 143 of FIG. 2 is disposed in atwo-dimensional procession (two-dimensional matrix) with pixels(unit-pixel) 11 comprising one piece each of conversion elements S1-1 toS6-6 which convert radiation into electric charges and switch elementsT1-1 to T6-6 which take out the electric charges from the conversionelements. In FIG. 2, for convenience, a total of 36 unit-pixels of sixby six pixels are illustrated.

This photoelectric conversion circuit unit 143 is, for example, formedon an insulating substrate such as glass by using an amorphous siliconthin film semiconductor, and the conversion elements S1-1 to S6-6 areformed by a MIS type structure based on amorphous silicon as a mainingredient. In this case, on the conversion elements S1-1 to S6-6, thewavelength converter 142 in which the conversion element convertsradiation into a light of the detectable wavelength region is provided,and the conversion element is incident with a visible light from thewavelength converter 142. Incidentally, the conversion elements S1-1 toS6-6 may be those absorbing the incident radiation (x-ray) andconverting it directly into an electric charge. As the main ingredientof the conversion element of this direct conversion type, for example,amorphous selenium, gallium arsenide, mercuric iodide, lead iodide orcadmium telluride can be cited. Further, as the switch elements T1-1 toT6-6, a TFT (thin film transistor) formed on the insulating substratesuch as glass by amorphous silicon is suitably used.

The conversion elements S1-1 to S6-6 comprise photodiodes, and areapplied with a reverse bias. That is, the cathode electrode side of thephotodiode is biased to +(plus). A bias wire Vs is a common wire, and isconnected to a reference power source circuit 12.

The drive wires G1 to G6 connect the switch element of each pixel in arow direction. The signal wires M1 to M6 connects the switch element ofeach pixel in a column direction. The drive circuit unit 101 supplies adrive signal (pulse) to each of the gate wires G1 to G6 so as to driveeach switch element, and drive-controls each of the conversion elementsS1-1 to S6-6.

The signal processing circuit unit 102 amplifies the electric chargeoutputted in parallel for every row from each pixel through each of thesignal wires M1 to M6, and subjects it to series conversion so as tooutput it as an analogue data (image data). The signal processingcircuit unit 102 comprises by including amplifiers A1 to A6 providedwith capacitors Cf1 to Cf6 provided between input and output terminals,respectively, various switches, sampling and holding circuit comprisingcapacitors CL1 to CL6, reference power source circuit 12, and analoguemultiplexer 13.

A switch RES is for resetting the capacitors Cf1 to Cf6. The amplifiersA1 to A6 is for amplifying the signal charges from the signal wires M1to M6. The capacitors CL1 to CL6 are sampling and holding capacitors fortemporarily storing the signal charges amplified by the amplifiers A1 toA6. A switch SMPL is for performing a sampling and holding. The analoguemultiplexer (MUX) 13 is for directly converting the signal chargeoutputted in parallel, and comprises by including an analogue shiftresistor (ASR) 110.

The imaging control unit 214, according to the photographing conditioninstructed from the system control unit 310, supplies a clock signal CLKto the analogue shift resistor 110 in the analogue multiplexer 13 of thesignal processing circuit unit 102. This clock signal CLK is a signalfor allowing the analogue shift resistor 110 to be shifted.

FIG. 3 is a timing chart illustrating a first method for driving(unit-pixel reading mode) of the radiation imaging apparatus 140. Basedon this timing chart, the operations of the photoelectric conversioncircuit unit 143, drive circuit unit 101, and signal processing circuitunit 102 illustrated in FIG. 2 will be described.

First, the operation in a photoelectric conversion period (x-rayirradiation period) will be described. In a state in which all theswitch elements are turned off, when radiation (x-ray) is irradiatedpulse-wise from the radiation generating apparatus 120, radiation or alight subjected to wavelength conversion from radiation is irradiated oneach conversion element, and signal electric charge corresponding toradiation or a light quantity is accumulated in each conversion element.

At this time, when the above described wavelength conversion member 143which converts the x-ray into a visible light is used, a member guidingthe visible light corresponding to the x-ray dose rate to the conversionelement side may be used or the wavelength conversion member 143 may bedisposed in the extreme vicinity of the conversion element.Incidentally, even after a light source is turned off, the signal chargesubjected to photoelectrical conversion is held in each conversionelement.

Next, the operation in the reading period will be described. The readingoperation is performed in order for the conversion elements S1-1 to S1-6of a first line, the conversion elements S2-1 to S2-6 of a second line,and the conversion elements S3-1 to S3-6 of a third line, and it isperformed until the reading operation of the conversion elements S6-1 toS6-6 of a sixth line.

First, to read the signal charges accumulated in the conversion elementsS1-1 to S1-6 of the first line, a drive signal is given to the drivewire G1 connected to the switch elements T1-1 to T1-6 of a first linefrom the drive circuit unit 101. At this time, the drive circuit unit101, based on a control from the imaging control unit 214, outputs thedrive signal to the drive wire G1. As a result, the switch elements T1-1to T1-6 of the first line are put into a turned on state, and the signalcharges accumulated in the conversion elements S1-1 to S1-6 of the firstline are transferred through the signal wires M1 to M6.

These transferred signal charges are amplified by the amplifiers A1 toA6 according to the capacitance of the capacitors Cf1 to Cf6. Theamplified signal charges are sampled and held in the capacitors CL1 toCL6 by the SMPL signal based on a control from the imaging control unit214. The signal charge of each of the capacitors CL1 to CL6 is outputtedin order from the capacitors CL1, CL2, CL3, CL4, CL5, and CL6 inproportion as the analogue shift resistors 110 are synchronized with theCLK signal based on a control from the imaging control unit 214, and areswitched on in order. As a result, the signal charges accumulated in theconversion elements S1-1 to S1-6 of the first line are outputted inorder as analogue data by the analogue multiplexer 13.

Similarly to the reading operation of the conversion elements S1-1 toS1-6 of the first line, the reading operations from the conversionelements S2-1 to S2-6 of the second line up to the conversion elementsS6-1 to S6-6 of the sixth line are performed in order.

Incidentally, if the signal charges from each of the signal wires M1 toM6 are sample-held in the capacitors CL1 to CL6 by the SMPL signal atthe reading time of the conversion elements of the first line, thecapacitors Cf1 to Cf6 are reset by the RES signal, and after that, thedrive signal can be applied to the drive wire G2. That is, during thesignal charges from the conversion elements of the first line aresubjected to series conversion operation by the analogue multiplexer 13,the signal charges of the conversion elements S2-1 to S2-6 of the secondline can be transferred at the same time. In this manner, the incidentradiation is converted into a light of the wavelength region detectableby the conversion element by using the wavelength converter 142, and thelight is converted into the electric charge by the conversion element,and the radiation information is read as the electrical signal, so thatthe image data of the subject can be obtained.

In the present embodiment, the reading mode by the signal processingcircuit unit 102 includes three reading modes of a unit-pixel readingmode, four-pixel-addition reading mode, and nine-pixel-addition readingmode. Each reading mode by this signal processing circuit unit 102 isperformed based on a control from the imaging control unit 214. Theunit-pixel reading mode, as described in FIG. 3, is a mode for readingthe signal charge from the conversion element for every one line bygiving the drive signal from the drive circuit unit 101 to every oneline in order.

FIG. 4 is a timing chart illustrating a second method for driving(four-pixel-addition reading mode) of the radiation imaging apparatus140.

The four-pixel-addition reading mode illustrated in FIG. 4 is a mode inwhich the signal charges in a total four unit-pixels of the unit-pixelsof two rows by two columns are bound and these signals are read as thesignal charge of one multi-pixel. In this case, in the presentembodiment, by a control from the imaging control unit 214, the drivesignals are given simultaneously to the drive wires of two lines fromthe drive circuit unit 101, and at the same time, in the signalprocessing circuit unit 102, the charge signals for two lines aresimultaneously read. After reading, the addition (digital addition) ofthe electric charges for two lines are performed. In FIG. 4, the drivesignals are given simultaneously to two lines each of each pair of drivewires G1 and G2, G3 and G4, and G5 and G6.

FIG. 5 is a timing chart illustrating a third method for driving(nine-pixel-addition reading mode) of the radiation imaging apparatus140.

The nine-pixel-addition reading mode illustrated in FIG. 5 is a mode inwhich the signal charges in a total nine unit-pixels of the unit-pixelsof three rows by three columns are bound and these signals are read asthe signal charge of one multi-pixel. In this case, in the presentembodiment, by a control from the imaging control unit 214, the drivesignals are given simultaneously to the drive wires of three lines fromthe drive circuit unit 101, and at the same time, in the signalprocessing circuit unit 102, the charge signals for three lines aresimultaneously read. After reading, the addition of the charge signalsfor three lines are performed. In FIG. 5, the drive signals are givensimultaneously to three lines each of each pair of drive wires G1, G2and G3, and G4, G5 and G6.

As illustrated in FIGS. 4 and 5, by addition and reading the pixels, thereading time is shortened, and a frame rate is increased at the movingimage radiographing time, and an S/N ratio is also improved.

Next, a method for extracting a defective pixel in the radiation imagingsystem of the present embodiment will be described. In the presentembodiment, as described above, the radiographing by three reading modesdescribed in FIGS. 3, 4, and 5 can be performed. In the radiationimaging system of the present embodiment, a defect coordinate tablecorresponding to each reading mode is, for example, stored in theexternal memory device 161, and when each reading mode is designatedfrom the imaging control unit 214, the radiographed image data iscorrected by using the corresponding defect coordinate table.

First, a production process of the defect coordinate table in theradiation imaging system of the present embodiment will be described.

FIG. 6 is a flowchart illustrating a production process of a defectcoordinate table used for the unit-pixel reading mode of FIG. 3. First,at step S101, the imaging control unit 214, with the radiographing modetaken as a unit-pixel reading defect extracting mode, allows radiationto be generated from the radiation generating apparatus 120 in a statein which the subject 126 does not exist between the radiation generatingapparatus 120 and the radiation imaging apparatus 140, and allows theradiation imaging apparatus 140 to perform radiographing. The imagingcontrol unit 214 performs a control for transferring the analogue dataof each unit-pixel read from the radiation imaging apparatus 140 by theradiographing to the image processing unit 10.

Subsequently, at step S102, the imaging control unit 214, controls theimage processing unit 10, and extracts the defect of the unit-pixel fromwithin the radiographed image data. Specifically, this extractionprocessing of the defect of the unit-pixel compares the output value ofeach read unit-pixel and a certain threshold value (predeterminedvalue), and extracts the unit-pixel whose output value is out of thethreshold value as a defect. In the present embodiment, when the outputvalue in the normal unit-pixel is taken as 100%, the threshold value ofthe output value is taken as 95%, and the unit-pixel whose output valueis below 95% is extracted as a defect.

Subsequently, at step S103, the imaging control unit 214, based on theextraction result of the defect unit-pixel, produces a unit-pixel defectcoordinate table including defect information (positional informationindicating row and column and the like) regarding the defect unit-pixel,and this table is stored in the external memory device 161. By goingthrough the processings of these steps S101 to S103, the defectinformation regarding the defect unit-pixel is stored in the externalmemory device 161.

FIG. 7 is a flowchart illustrating a production process of the defectcoordinate table used for the four-pixel-addition reading mode of FIG.4. First, at step S201, the imaging control unit 214, with theradiographing mode taken as the four-pixel-addition reading defectextracting mode, allows radiation to be generated from the radiationgenerating apparatus 120 in a state in which the subject 126 does notexist between the radiation generating apparatus 120 and the radiationimaging apparatus 140, and allows the radiation imaging apparatus 140 toperform radiographing. The imaging control unit 214 performs a controlfor transferring the analogue data in the multi-pixel for the fourunit-pixels read from the radiation imaging apparatus 140 by theradiographing to the image processing unit 10.

Subsequently, at step S202, the imaging control unit 214 controls theimage processing unit 10 and extracts the defects of the multi-pixelfrom within the radiographed image data. Specifically, this extractionprocessing of the defects of the multi-pixel compares the output valueof each of the read multi-pixel and a certain threshold value(predetermined value), and extracts the multi-pixel whose output valueis out of the threshold value as defects. In the present embodiment,when the output value in the normal multi-pixel is taken as 100%, thethreshold value of the output value is taken as 95%, and the multi-pixelwhose output value is below 95% are extracted as the defects.

Subsequently, at step S203, the imaging control unit 214, based on theextraction result of the defective multi-pixel, produces a defectcoordinate table of the multi-pixel by the four-pixel-addition includingthe defect information (positional information indicating row and columnand the like) regarding the defective multi-pixel, and this table isstored in the external memory device 161. By going through theprocessings these steps S201 to S203, the defect information regardingthe multi-pixel by the four-pixel-addition is stored in the externalmemory device 161.

FIG. 8 is a flowchart illustrating the production process of the defectcoordinate table used for the nine-pixel-addition reading mode of FIG.5.

First, at step S301, the imaging control unit 214, with theradiographing mode taken as the nine-pixel-addition reading defectextracting mode, allows radiation to be generated from the radiationgenerating apparatus 120 in a state in which the subject 126 does notexist between the radiation generating apparatus 120 and the radiationimaging apparatus 140, and allows the radiation imaging apparatus 140 toperform radiographing. The imaging control unit 214 performs a controlfor transferring the analogue data in the multi-pixel for the nineunit-pixels read from the radiation imaging apparatus 140 by theradiographing to the image processing unit 10.

Subsequently, at step S302, the imaging control unit 214 controls theimage processing unit 10 and extracts the defects of the multi-pixelfrom within the radiographed image data. Specifically, this extractionprocessing of the defects of the multi-pixel compares the output valueof each of the read multi-pixel and a certain threshold value(predetermined value), and extracts the multi-pixel whose output valueis out of the threshold value as defects. In the present embodiment,when the output value in the normal multi-pixel is taken as 100%, thethreshold value of the output value is taken as 95%, and the multi-pixelwhose output value is below 95% are extracted as the defects.

Subsequently, at step S303, the imaging control unit 214, based on theextraction result of the defective multi-pixel, produces the multi-pixeldefect coordinate table by the nine-pixel-addition including the defectinformation (positional information indicating row and column and thelike) regarding the defective multi-pixel, and this table is stored inthe external memory device 161. By going through the processings ofthese steps S301 to S303, the defect information regarding themulti-pixel by the nine-pixel-addition is stored in the external memorydevice 161.

Incidentally, the extraction processing of the defects illustrated inFIGS. 6 to 8, for example, may be performed at the factory shipment timeof the radiation imaging apparatus 143. Further, the defect extractingmode is different from the normal radiographing mode, and it is a modein which the output value of each read pixel and a certain threshold(predetermined value) are compared, and the pixel whose output value isout of the threshold value is extracted as a defect. That is, the defectextracting mode allows radiation from the radiation generating apparatus120 to be irradiated on the photoelectric conversion circuit unit 143 ina state in which the subject 126 does not exist between the radiationgenerating apparatus 120 and the radiation imaging apparatus 140, andreads the electric charge of each pixel, and loads it to the imageprocessing unit 10 as an image data, and determines whether or not theeach pixel is defective based on a certain threshold value. The pixeldetermined as defective has its positional information (information onrow and column and the like) stored in the defect coordinate table.

FIGS. 9A and 9B a reviews illustrating the defect unit-pixel when theradiation imaging apparatus of FIG. 2 is read by the unit-pixel readingmode and one example of the unit-pixel defect coordinate table. Here, inFIG. 9A, the position of the defect unit-pixel when read by theunit-pixel reading mode is illustrated, and in FIG. 9B, one example ofthe unit-pixel defect coordinate table is illustrated. In the presentexample, as shown in FIGS. 9A and 9B, the defect unit-pixels asillustrated in A to C exist.

FIGS. 10A and 10B are views illustrating the defective multi-pixel whenthe radiation imaging apparatus of FIG. 2 is read by thefour-pixel-addition mode and one example of the multi-pixel defectcoordinate table by the four-pixel-addition. Here, in FIG. 10A, thepositions of the defective multi-pixel when read by thefour-pixel-addition reading mode are illustrated, and in FIG. 10B, oneexample of the coordinate table of the defective multi-pixel by thefour-pixel-addition is illustrated. To perform the four-pixel-additionreading, as illustrated in FIG. 10A, the unit-pixel 11 of two rows bytwo columns is equivalent to one multi-pixel 21, and the image dataoutputted from the radiation imaging apparatus 140 becomes the data of atotal of nine multi-pixel 21 of three rows by three columns. In thepresent example, as illustrated in FIGS. 10A and 10B, the defectivemulti-pixel 21 as illustrated in A and B exist.

FIGS. 11A and 11B are views illustrating the defective multi-pixel whenthe radiation imaging apparatus of FIG. 2 is read by thenine-pixel-addition reading mode and one example of the multi-pixeldefect coordinate table by the nine-pixel-addition. Here, in FIG. 11A,the position of the defective multi-pixel when read by thenine-pixel-addition mode is illustrated, and in FIG. 11B, one example ofthe multi-pixel defect coordinate table by the nine-pixel-addition isillustrated. To perform the nine-pixel-addition reading, as illustratedin FIG. 11A, the unit-pixel 11 of three rows by three columns isequivalent to one multi-pixel 31, and the image data outputted from theradiation imaging apparatus 140 is the data of a total of fourmulti-pixel 31 of two rows by two columns. In the present example, asillustrated in FIGS. 11A and 11B, the defective multi-pixel 31 asillustrated by A exists.

As illustrated in FIGS. 9A to 11B, as the number of the pixel-additionincreases, so the number of the defects decreases. This will bedescribed below.

In the case of the four-pixel-addition reading mode illustrated in FIG.10A, four unit-pixels 11 for two rows by two columns are read as onemulti-pixel 21. Hence, the output value of the multi-pixel 21 becomessimply four times that of the unit-pixel 11. Further, an effect occupiedby each unit-pixel 11 in one multi-pixel 21 is ¼ (25%). Similarly, inthe case of the nine-pixel-addition reading mode illustrated in FIG.11A, nine unit-pixels 11 for three rows by three columns are read as onemulti-pixel 31, and therefore, the output value of the multi-pixel 31becomes simply nine times that of the unit-pixel 11. Further, an effectoccupied by each unit-pixel 11 in one multi-pixel 31 is 1/9 (11%).

In this manner, in the pixel-addition reading, as the number of thepixel-addition increases, so a ratio occupied by the effect of eachunit-pixel 11 decreases, and an effect of the defect of the unit-pixel11 is hard to be received. Hence, depending on the defect of theunit-pixel, there are often the cases where such defect is no longer thedefect as the multi-pixel by performing the pixel-addition reading.Thus, in the present embodiment, the defect coordinate table forperforming the correction of the defect of the pixel is also preparedfor each pixel-addition mode, and is stored, and when radiographing thesubject, the correction of the defect of the pixel is performed byreferring to the defect coordinate table corresponding to eachpixel-addition reading mode.

In the present embodiment, the threshold value when extracting thedefect is taken as a pixel whose output value is reduced not less than5% for average of the entire surface, in other words, whose output valueis below 95% for average of the entire surface.

As illustrated in FIGS. 9A and 9B, in case of reading by the unit-pixelreading mode, the defective unit-pixel exists in a total of three piecesof A to C. As against the output value of the normal unit-pixel, theoutput value of the unit-pixel A is 50% (reduced by 50%), the outputvalue of the unit-pixel B is 70% (reduced by 30%), and the output valueof the unit-pixel C is 90% (reduced by 10%), and each output value isfar below the threshold value, and therefore, each unit-pixel isextracted as the defective unit-pixel. The defect information regardingthese defective unit-pixels A to C is registered in the unit-pixeldefect coordinate table of FIG. 9B. Here, in the present embodiment, theunit-pixel other than the defective unit-pixels A to C is taken as anormal pixel and its output value is taken as an average (reduced by0%).

As illustrated in FIGS. 10A and 10B, in case of reading by thefour-pixel-addition reading mode, the defective multi-pixel exist in atotal of two pieces of A and B. The detective unit-pixel C illustratedin FIGS. 9A and 9B has 90% (reduced by 10%) of the output value in theunit-pixel reading mode, and is defective. In the four-pixel-additionreading mode, since the reduction in the output value in the other threeunit-pixels except for the defective unit-pixel C is 0%, the outputvalue of the multi-pixel 21 including this defective unit-pixel C is90%+100%+100%+100%=390%. In the case of the four-pixel-addition reading,as compared with the unit-pixel reading, the output value is a normalvalue of 400% which is 4 times that of the unit-pixel reading, and theoutput value of the multi-pixel 21 including the defective unit-pixel Cis an output value of 390%/400%=97% as against the output value of thenormal multi-pixel 21. Hence, this value satisfies a value within 5%which is the threshold value of the defect extraction, and therefore,the multi-pixel 21 including the defective unit-pixel C is not defectivein the four-pixel-addition reading mode.

On the other hand, the multi-pixel 21 (multi-pixel A) including adefective unit-pixel A of FIGS. 9A and 9B becomes an output value of50%+100%+100%+100%=350%, and becomes an output value of 350%/400%=87% asagainst the normal multi-pixel 21, and therefore, does not come within5% of the threshold value, and is extracted as defective. Further, themulti-pixel 21 (multi-pixel B) including the defective unit-pixel B ofFIGS. 9A and 9B becomes the output value of 70%+100%+100%+100%=370%, andbecomes the output value of 370%/400%=92% as against the normalmulti-pixel 21, and therefore, it does not come within 5% of thethreshold value, and is extracted as defective. The defectiveinformation regarding these defective multi-pixel A and B is registeredin the multi-pixel defect coordinate table by the four-pixel-additionreading of FIG. 10B. In this manner, the number of defects of thefour-pixel-addition reading mode is a total of two pieces, and this isshort of one piece when compared with the unit-pixel reading mode.

Similarly, as illustrated in FIGS. 11A and 11B, in case of reading bythe nine-pixel-addition reading mode, the multi-pixel 31 (multi-pixel A)including the defective unit-pixel A of FIGS. 9A and 9B becomes theoutput value of 50%+100%×8=850%. Since this multi-pixel A becomes theoutput value of 850%/900%=94% as against the normal multi-pixel 31, itdoes not come within 5% of the threshold value, and is extracted asdefective. Further, the multi-pixel 31 including the defectiveunit-pixel B of FIGS. 9A and 9B becomes the output value of70%+100%×8=870%, and becomes the output value of 870%/900%=96% asagainst the normal multi-pixel 31, and therefore, comes within 5% of thethreshold value, and does not become defective. Further, the multi-pixel31 including the defective unit-pixel C of FIGS. 9A and 9B becomes theoutput value of 90%+100%×8=890%, and becomes the output value of890%/900%=98% as against the normal multi-pixel 31, and therefore, itcomes within 5% of the threshold value, and does not become defective.As a result, in the nine-pixel-addition reading mode, the multi-pixel Aonly is registered in the multi-pixel defect coordinate table by thenine-pixel-addition as defective.

In this manner, in the present embodiment, the defect coordinate tableis prepared in three types and is stored according to the reading modeof the pixel, and at the time of radiographing the object, the defectcoordinate table corresponding to the reading mode of each pixel isreferred to, and the defect correction of the image data is performed.By preparing the defect coordinate table for each pixel reading mode inthis manner, the number of defects can be reduced at the pixel-additiontime.

Next, a method for correction processing of the defective pixel in theradiation imaging system of the present embodiment will be described.

FIG. 12 is a flowchart illustrating the correction processing of thedefective pixel in the radiation imaging system according to the firstembodiment. When a radiographing mode (pixel reading mode) is selectedby an operator 305, the system control unit 310 instructs aradiographing condition based on the selected radiographing mode for theimaging control unit 214, and the imaging control unit 214 performs theradiographing of the object based on the radiographing condition (stepS401).

After completing the radiographing, at step S402, the imaging controlunit 214 controls the image processing unit 10 and performs an offsetcorrection of the image data radiographed by the radiation imagingapparatus 140.

Subsequently, at step S403, the imaging control unit 214 determineswhether or not the radiographing mode (pixel reading mode) selected atstep S401 is the unit-pixel reading mode. As a result of thisdetermination, when the selected radiographing mode is a unit-pixelreading mode, the procedure advances to step S404. Then, at step S404,the imaging control unit 214 controls the image processing unit 10 andperforms the defect correction of the image data radiographed by theradiation imaging apparatus 140 by using the unit-pixel defectcoordinate table stored in the external memory device 161. On the otherhand, as a result of the determination at step S403, when the selectedradiographing mode is not the unit-pixel reading mode, the procedureadvances to step S405.

Subsequently, at step S405, the imaging control unit 214 determineswhether or not the radiographing mode (pixel reading mode) selected atstep S401 is the four-pixel-addition reading mode. As a result of thisdetermination, when the selected radiographing mode is thefour-pixel-addition reading mode, the procedure advances to step S406.Then, at step S406, the imaging control unit 214 controls the imageprocessing unit 10 and performs the defect correction of the image dataradiographed by the radiation imaging apparatus 140 by using themulti-pixel defect coordinate table by the four-pixel-addition stored inthe external memory device 161. On the other hand, as a result of thedetermination at step S405, when the selected radiographing mode is notthe four-pixel-addition reading mode, the procedure advances to stepS407.

Subsequently, at step S407, the imaging control unit 214 determineswhether or not the radiographing mode (pixel reading mode) selected atstep S401 is the nine-pixel-addition reading mode. As a result of thisdetermination, when the selected radiographing mode is thenine-pixel-addition reading mode, the procedure advances to step S408.Then, at step S408, the imaging control unit 214 controls the imageprocessing unit 10 and performs the defect correction of the image dataradiographed by the radiation imaging apparatus 140 by using themulti-pixel defect coordinate table by the nine-pixel-addition stored inthe external memory device 161. On the other hand, as a result of thedetermination at step S407, when the selected radiographing mode is notthe nine-pixel-addition reading mode, the procedure advances to stepS409.

When the processings of steps S404, S406, and S408 are completed or atstep S407, when it is determined that the selected radiographing mode isnot the nine-pixel-biding reading mode, subsequently, at step S409, theimaging control unit 214 controls the image processing unit 10 andperforms a white correction for the image data.

Subsequently, at step S410, the image data processed at the imageprocessing unit 10 is displayed at the display unit 160 as an image.

By going through the processings of the above described steps S401 toS410, the correction processing of the defective pixel of the image dataradiographed by the radiation imaging apparatus 140 is performed.

Here, in the present embodiment, though the image processing unit 10 isdisposed separately from the radiation imaging apparatus 140, thepresent invention is not limited to this, the image processing unit 10may be disposed within the radiation imaging apparatus 140. Further, inthe present embodiment, though the defect coordinate table correspondingto respective pixel reading modes is stored in the external memorydevice 161, the present invention is not limited to this, and eachdefect coordinate table may be stored in storage means provided withinthe radiation imaging apparatus 140. Further, the image processing unit10 and the storage means having the defect coordinate table may beprovided within the radiation imaging apparatus 140, and the imageprocessing such as the offset correction, white correction, and defectcorrection may be performed within the radiation imaging apparatus 140.

Further, in the present embodiment, though a description has been madeon the pixel-addition reading mode by taking the four-pixel-additionreading mode and the nine-pixel-addition reading mode as the examples,the present invention is not limited to this, and any other additionreading mode can be also applied to the invention.

SECOND EMBODIMENT

Next, a second embodiment of the present invention will be described.Since the configuration of a radiation imaging system according to thesecond embodiment is the same as the configuration of the radiationimaging system according to the first embodiment illustrated in FIG. 1,the description thereof will be omitted. The radiation imaging systemaccording to the second embodiment is different in a method forextracting a defective pixel as against the radiation imaging systemaccording to the first embodiment, and therefore, the description on themethod alone will be made. At this time, in the second embodiment, adescription will be made by an example in which the photoelectricconversion circuit unit 143 illustrated in FIG. 2 comprises a total of64 pieces of eight by eight pixels of the unit-pixel.

FIG. 13 is a flowchart illustrating a method for extracting a defectivepixel in the radiation imaging system according to the secondembodiment.

In the first embodiment, though the radiographing is performed by thedefect extracting mode for each pixel reading method, in the secondembodiment, the radiographing only of a defect extracting mode byunit-pixel reading is performed. Specifically, the radiographing by thedefect extracting mode by the unit-pixel reading is performed, andfour-pixel-addition and 16-pixel-addition are performed for the data(output value) of each unit-pixel, and the defect extracting in eachmulti-pixel when performing the reading by each pixel-addition readingmode is performed. This is a processing equivalent to (convert intoimage data by four-pixel-addition) and (convert into image data by16-pixel-addition) of the flowchart illustrated in FIG. 13.

First, at step S501, the imaging control unit 214 takes a radiographingmode as a unit-pixel reading defect extracting mode, and allowsradiation to be generated from a radiation generating apparatus 120 in astate in which no subject 126 exists between the radiation generatingapparatus 120 and a radiation imaging apparatus 140, and allows theradiation imaging apparatus 140 to perform radiographing. The imagingcontrol unit 214 performs a control for transferring the analogue dataof each unit-pixel read from the radiation imaging apparatus 140 by theradiographing to an image processing unit 10.

Subsequently, at step S502, the imaging control unit 214 controls theimage processing unit 10 and extracts the defect of the unit-pixel fromwithin the radiographed image data. Specifically, this extractingprocessing of the unit-pixel defect compares the output value of eachread unit-pixel and a certain threshold value (predetermined value), andextracts the unit-pixel whose output value is out of the threshold valueas a defect. In the present embodiment, when the output value in thenormal unit-pixel is taken as 100%, the threshold value of the outputvalue is taken as 95%, and the unit-pixel whose output value is below95% is extracted as a defect. At this time, for example, the outputvalue of each unit-pixel is stored in the memory within the imageprocessing unit 10.

Subsequently, at step S503, the imaging control unit 214, based on theextraction result of the defective unit-pixel, produces the unit-pixeldefect coordinate table including defect information (positionalinformation indicating row and column and the like) regarding thedefective unit-pixel, and this table is stored in an external memorydevice 161.

Subsequently, at step S504, by arithmetically processing the outputvalue of each unit-pixel stored in the memory within the imageprocessing unit 10, the output value is converted into the image datawhen performing the four-pixel-addition reading. The image data at thistime is a data taking unit-pixels 11 of two rows by two columns as onemulti-pixel.

Subsequently, at step S505, the imaging control unit 214 controls theimage processing unit 10, and extracts the defect of the multi-pixelfrom within the image data converted at step S504. Specifically, theextracting processing of this multi-pixel defect compares the outputvalue of each multi-pixel and a certain threshold value (predeterminedvalue), and extracts the multi-pixel whose output value is out of thethreshold value as a defect. In the present embodiment, when the outputvalue in the normal multi-pixel is taken as 100%, the threshold value ofthe output value is taken as 95%, and the multi-pixel whose output valueis below 95% is extracted as a defect.

Subsequently, at step S506, the imaging control unit 214, based on theextraction result of the defective multi-pixel at step S505, produces amulti-pixel defect coordinate table by the four-pixel-addition includingthe defect information regarding the defective multi-pixel and thistable is stored in the external memory device 161.

Subsequently, at step S507, by arithmetically processing the outputvalue of each unit-pixel stored in the memory within the imageprocessing unit 10, this output value is converted into the image datawhen performing the 16-pixel-addition reading. The image data at thistime is a data taking the unit-pixels 11 of four rows by four columns asone multi-pixel.

Subsequently, at step S508, the imaging control unit 214 controls theimage processing unit 10, and extracts the defect of the multi-pixelfrom within the image data converted at step S507. Specifically, theextracting processing of this multi-pixel defect compares the outputvalue of each multi-pixel and a certain threshold value (predeterminedvalue), and extracts the multi-pixel whose output value is out of thethreshold value as a defect. In the present embodiment, when the outputvalue in the normal multi-pixel is taken as 100%, the threshold value ofthe output value is taken as 95%, and the multi-pixel whose output valueis below 95% is extracted as a defect.

Subsequently, at step S509, the imaging control unit 214, based on theextraction result of the defective multi-pixel at step S508, produces amulti-pixel defect coordinate table by the 16-pixel-addition includingthe defect information regarding the defective multi-pixel and thistable is stored in the external memory device 161.

By going through the processings of the above described steps S501 toS509, one time radiographing by the defect extracting mode by theunit-pixel reading can produce the pixel defect coordinate table by eachreading mode (unit-pixel, four-pixel-addition, and 16-pixel-addition).

In the second embodiment, since the radiographing by the defectextracting mode in the unit-pixel reading is performed one time only, anadvantage is afforded in that the work load of an operator 305performing the radiographing can be reduced as compared with the firstembodiment.

FIGS. 14A and 14B are views illustrating the output value in eachunit-pixel 11 and one example of the unit-pixel defect coordinate table.Here, in FIG. 14A, the output value in each unit-pixel 11 and theposition of the defective pixel are illustrated, and in FIG. 14B, oneexample of the unit-pixel defect coordinate table is illustrated. In thepresent embodiment, as illustrated in FIGS. 14A and 14B, the defectunit-pixels as illustrated in A to C exist.

FIGS. 15A and 15B are views illustrating the output value of eachmulti-pixel 41 by the four-pixel-addition and one example of themulti-pixel defect coordinate table by the four-pixel-addition. Here, inFIG. 15A, the output value in each multi-pixel 41 by thefour-pixel-addition and the position of the defective pixel areillustrated, and in FIG. 15B, one example of the multi-pixel defectcoordinate table by the four-pixel-addition is illustrated. To performthe four-pixel-addition, as illustrated in FIG. 15A, the unit-pixels 11of two rows by two columns are equivalent to one multi-pixel 41, and theimage data becomes a data of a total 16 pieces of multi-pixels 41 offour rows by four columns. In the present example, as illustrated inFIGS. 15A and 15B, the defective multi-pixel 41 illustrated in B and Cexists.

FIGS. 16A and 16B are views illustrating the output value of eachmulti-pixel 51 by 16-pixel-addition and one example of the multi-pixeldefect coordinate table by the 16-pixel-addition. Here, in FIG. 16A, theoutput value in each multi-pixel 51 by the 16-pixel-addition and theposition of the defective pixel are illustrated, and in FIG. 16B, oneexample of the multi-pixel defect coordinate table by the16-pixel-addition is illustrated. To perform the 16-pixel-addition, asillustrated in FIG. 16A, the unit-pixels 11 of four rows by four columnsare equivalent to one multi-pixel 51, and the image data becomes a dataof the multi-pixels 51 of a total four pieces of two rows by twocolumns. In the present example, as illustrated in FIGS. 16A and 16B,there exists no defective multi-pixel.

FIG. 15A is a view for addition the output values of the unit-pixels 11of two rows by two columns of FIG. 14A, and FIG. 16A is a view foraddition the output values of the unit-pixels 11 of four rows by fourcolumns of FIG. 14A. The threshold value of the defective pixel in thesecond embodiment is a pixel of the output value below 95% as againstthe output value of the normal pixel.

In the unit-pixel reading mode, though the three defect unit-pixels 11of A to C exist, at the four-pixel-addition time, the multi-pixel 41including this defective unit-pixel A becomes non-defective by thefour-pixel-addition due to the effect of the peripheral pixel, andtherefore, it is excluded from the defective pixel. Here, at thefour-pixel-addition time, the output value 100×4=400 is an average andthe output value 400×0.95=380 becomes a threshold value of the defectivepixel. Further, in the 16-pixel-addition, the multi-pixel 51 includingthe defective unit-pixel B and the multi-pixel 51 including thedefective unit-pixel C are also non-defective, and the defect becomeszero. Here, at the 16-pixel-addition time, the output value 100×16=1600is an average and the output value 1600×0.95=1520 becomes a thresholdvalue of the defective pixel.

By providing the defect coordinate table for each pixel-addition mode inthis manner, the number of defective pixel data is reduced, and thedeterioration of the image quality can be reduced.

Further, in the present embodiment, though a description has been madeon the pixel-addition reading mode by taking the four-pixel-additionreading mode and the 16-pixel-addition reading mode as the example, thepresent invention is not limited to this, and any other addition readingmode can be also applied to the invention.

THIRD EMBODIMENT

Next, a third embodiment of the present invention will be described.Since the configuration of a radiation imaging system according to thethird embodiment is the same as the configuration of the radiationimaging system according to the second embodiment, the descriptionthereof will be omitted. The radiation imaging system according to thethird embodiment is different from the radiation imaging systemaccording to the second embodiment in that a method for extracting adefective pixel is different, and therefore, a description will be madeonly on that method.

FIG. 17 is a flowchart illustrating a method for extracting a defectivepixel in the radiation imaging system according to the third embodiment.

In the second embodiment, the radiographing of a defect extracting byunit-pixel reading is performed, and by the image processing, images byfour-pixel-addition and nine-pixel-addition are produced, therebyperforming the extracting of the defect. On the other hand, in the thirdembodiment, a threshold value is changed from the image by theunit-pixel reading, and the extraction of defect of each pixel-additionmode is performed.

First, the imaging control unit 214, with the radiographing mode takenas a unit-pixel reading defect extracting mode, allows radiation to begenerated from a radiation generating apparatus 120 in a state in whichno subject 126 exists between the radiation generating apparatus 120 anda radiation imaging apparatus 140, and allows the radiation imagingapparatus 140 to perform the radiographing. The imaging control unit 214performs a control for transferring the analogue data of each unit-pixelread from the radiation imaging apparatus 140 by the radiographing to animage processing unit 10.

Subsequently, the imaging control unit 214 controls an image processingunit 10, and extracts the defect of a unit-pixel from within theradiophotographed image data. Specifically, the extracting processing ofthis unit-pixel defect compares the output value of each read unit-pixeland a certain threshold value (predetermined value), and extracts theunit-pixel whose output value is out of the threshold value as a defect.In the present embodiment, when the output value in the normalunit-pixel is taken as 100%, the threshold value of the output value istaken as 90%, and the unit-pixel whose output value is below 90% isextracted as a defect. At this time, for example, the output value ofeach unit-pixel is stored in a memory within the image processing unit10.

Subsequently, the imaging control unit 214, based on the extractionresult of the defective unit-pixel, produces a unit-pixel defectcoordinate table including defect information (positional informationindicating row and column and the like) regarding the defectiveunit-pixel, and this table is stored in an external memory device 161.

Subsequently, the imaging control unit 214 controls the image processingunit 10, and extracts a four-pixel-addition defect from within theradiophotographed image data. Specifically, the extracting processing ofthis four-pixel-addition defect compares the output value of each readunit-pixel and a certain threshold value (predetermined value), andextracts the unit-pixel whose output value is out of the threshold valueas a defect. In the present embodiment, when the output value in thenormal unit-pixel is taken as 100%, the threshold value of the outputvalue is taken as 60%, and the unit-pixel whose output value is below60% is extracted as a defect. At this time, for example, the outputvalue of each unit-pixel is stored in a memory within the imageprocessing unit 10.

Subsequently, the imaging control unit 214, based on the extractionresult of the defective unit-pixel, produces a four-pixel-additiondefect coordinate table including defect information (positionalinformation indicating row and column and the like) regarding thedefective unit-pixel, and this table is stored in the external memorydevice 161.

Subsequently, the imaging control unit 214 controls the image processingunit 10, and extracts a nine-pixel-addition defect from within theradiophotographed image data. Specifically, the extracting processing ofthis nine-pixel-addition defect compares the output value of each readunit-pixel and a certain threshold value (predetermined value), andextracts the unit-pixel whose output value is out of the threshold valueas a defect. In the present embodiment, when the output value in thenormal unit-pixel is taken as 100%, the threshold value of the outputvalue is taken as 10%, and the unit-pixel whose output value is below10% is extracted as a defect. At this time, for example, the outputvalue of each unit-pixel is stored in the memory within the imageprocessing unit 10.

Subsequently, the imaging control unit 214, based on the extractionresult of the defective unit-pixel, produces a nine-pixel defectcoordinate table including defect information (positional informationindicating row and column and the like) regarding the defectiveunit-pixel, and this table is stored in the external memory device 161.

By going through the above described steps, one time radiographing bythe defect extracting mode by the unit-pixel reading can produce a pixeldefect coordinate table by each reading mode (unit-pixel,four-pixel-addition, and nine-pixel-addition).

In the third embodiment, since the radiographing by the defectextracting mode in the unit-pixel reading is performed one time only, anadvantage is afforded in that the work load of an operator 305performing the radiographing can be reduced as compared with the firstembodiment. Further, as compared with the second embodiment, since thereis no need to generate the pixel-addition image, the processing can bemade simple.

Further, in the third embodiment, as the pixel-addition increases, sothe effect of the unit-pixel to the multi-pixel decreases, andtherefore, the threshold value is changed for each pixel-addition mode,and the defect is extracted. For example, in the four-pixel-addition, anoccupied ratio of the multi-pixel to the output value of the unit-pixelbecomes one fourth. Hence, the threshold value can be made four timeslarger than the defect of the unit-pixel mode. For example, in theunit-pixel mode, though the pixel (threshold value 90%) whose output isreduced by 10% than the normal pixel is taken as a defect, in thefour-pixel-addition, the pixel (threshold value 60%) whose output isreduced by 40% than the normal pixel can be taken as a defect. Further,in the nine-pixel-addition, a ratio occupied by the unit-pixel becomesone ninth, and therefore, the pixel (threshold value 10%) whose outputis reduced by 90% is taken as a defect.

Further, in the third embodiment, though a description has been made onthe pixel-addition reading mode by taking the four-pixel-additionreading mode and the nine-pixel-addition reading mode as the example,the present invention is not limited to this, and any other additionreading mode can be also applied to the invention.

According to the first to third embodiments of the present invention,since the defect information corresponding to the method for reading thepixel in the conversion unit is stored, by using the defect informationon the pixel corresponding to the method for reading the pixel in theconversion unit, the correction of the defective pixel can be performed.As a result, an imaging apparatus (imaging system), a method forprocessing thereof, and a readable memory device for storing a programcan be provided, which reduces the defective pixel at the time of thepixel-addition reading and is more numerous in the pixel information inthe image data, and moreover, scarcely deteriorates in resolution of theimage data.

Next, in the fourth to sixth embodiments described below, a descriptionwill be made on a gain correction in case of performing thepixel-addition. The problem area of the gain correction in case ofperforming the pixel-addition as found by the inventor will be describedbelow.

As described earlier, the gain correction is a processing for correctingfluctuation of the sensitivity of a photoelectric conversion element andgain fluctuation of a signal processing circuit unit. This gaincorrection usually irradiates radiation and performs radiographing in astate in which no subject exists before radiographing the subject, andperforms a division processing for the image which has radiophotographedthe subject by using the radiophotographed image as a gain correctionimage.

When the pixel-addition reading is performed in the radiation imagingapparatus of the present invention, for example, there is a problem inthat the image after correction used actually by a doctor in hisdiagnosis is affected not only by the S/N of the subject image, but alsoby the S/N of the gain correction image. Further, there is a problem inthat, when a component other than the gain correction image mixes withthe gain correction image, this emerges in the image after correction asan artifact.

The fourth to sixth embodiments described below have been carried out inview of the above described problems, and these embodiments aim atproviding a radiation imaging apparatus, which is high in S/N whenperforming the gain correction in the radiographing by thepixel-addition, and moreover, realizes acquisition of a radiographedimage small in artifact.

FOURTH EMBODIMENT

FIG. 18 is an equivalent circuit diagram illustrating a detailedconfiguration in a radiation imaging apparatus 140 of a radiationimaging system according to a fourth embodiment.

Here, in FIG. 18, from among each component comprising the radiationimaging apparatus 140, a photoelectric conversion circuit unit 143, adrive circuit unit 146 provided in an external circuit unit 145, signalprocessing circuit unit 147, and a power source circuit unit 148 areillustrated. The photoelectric conversion circuit unit 143, drivecircuit unit 146, signal processing circuit unit 147, and the powersource circuit unit 148 illustrated in FIG. 18, for example, areconfigured by using an amorphous silicon thin film semiconductor.

This radiation imaging apparatus 140, based on a control from an imagingcontrol unit 214, is configured to be able to drive in various types ofoperation modes including a moving image radiographing mode and a stillimage radiographing mode.

The photoelectric conversion circuit unit 143 of FIG. 18 is disposed ina two-dimensional matrix pattern with photoelectric conversion elementsS1-1 to S8-8 which are conversion elements for converting radiation intoan electric signal (electric charge) and elements (unit-pixel) 100provided with one piece each of switch elements T1-1 to T8-8 for takingout (transferring) the electric signal from the photoelectric conversionelement. In FIG. 18, for convenience, a total of 64 unit-pixels of eightby eight pixels are illustrated.

Each unit-pixel 100 of this photoelectric conversion circuit unit 143,for example, is formed on an insulating substrate such as glass by usingthe amorphous silicon thin film semiconductor. Further, thephotoelectric conversion elements S1-1 to S8-8 are formed by a MIS typestructure or PIN type structure based on amorphous silicon as a mainingredient. In this case, on the photoelectric conversion elements S1-1to S8-8, a wavelength converter 142 in which the photoelectricconversion element converts radiation into a light of the detectablewavelength region is provided, and the photoelectric conversion elementis incident with a visible light from the wavelength converter 142.Incidentally, the photoelectric conversion elements S1-1 to S8-8 may bethose absorbing the incident radiation (x-ray) and converting itdirectly into an electric charge. As the photoelectric conversionelement of this direct conversion type, for example, one type selectedfrom among amorphous selenium, gallium arsenide, mercuric iodide, leadiodide, and cadmium telluride is made as a main ingredient. Further, asthe switch elements T1-1 to T8-8, a TFT (thin film transistor) formed onan insulating substrate such as glass by amorphous silicon is suitablyused.

The photoelectric conversion elements S1-1 to S8-8, for example,comprise photodiodes, and are applied with a reverse bias. That is, thecathode electrode side of the photodiode is biased to +(plus). A biaswire Vs is a common wire for supplying a bias (Vs) to each photo diode,and is connected to a power source circuit unit 148.

Gate wires G1 to G8 are wires for connecting a switch element of eachpixel in a row direction, and for turning on and off each of the switchelements T1-1 to T8-8. The drive circuit unit 146 applies a drive signal(pulse) to the gate wires G1 to G8 and drive-controls the switchelements T1-1 to T8-8. Signal wires M1 to M8 are wires for connectingthe switch element of each pixel in a column direction and reading theelectric signals (electric charges) of the photoelectric conversionelements S1-1 to S8-8 toward the signal processing circuit unit 147through the switch elements T1-1 to T8-8.

A switch RES is for resetting capacitors Cf1 to Cf8. The amplifiers A1to A8 is for amplifying electric signals from the signal wires M1 to M8.A Vref wire is a wire for supplying a reference power source from apower source circuit unit 104 to amplifiers A1 to A4. Capacitors CL1 toCL8 are sampling and holding capacitors for temporarily storing theelectric signals amplified by the amplifiers A1 to A8. A switch SMPL isfor performing a sampling and holding. Switches AVE1 and AVE2 are forpixel-addition (averaging out) the sampled and held electric signals. ADconverters AD1 to AD8 are for converting the electric signals (analoguesignals) sampled and held by the sampling and holding capacitors CL1 toCL8 into digital signals. These digital signals after AD conversion areoutputted, for example, to the image processing unit 10, and aresubjected to the predetermined processing such as image processing, andafter that, displaying and storing of the processed image data areperformed.

Next, the operation of the radiation imaging system according to thepresent embodiment will be described. FIG. 19 is a view illustrating theoperation mode of the radiation imaging system according to the fourthembodiment. As illustrated in FIG. 19, the radiation imaging systemaccording to the present embodiment is configured to be able to set fouroperation modes of a still image radiographing mode, a first movingimage radiographing mode (1), a second moving image radiographing mode(2), and a third moving image radiographing mode (3).

In the still image radiographing mode, since an image is radiographedonly one sheet, there is no need to quicken a frame rate, and yet aresolving power is required, and therefore, no addition drive of theunit-pixel is performed. Further, the moving radiographing mode has atotal of three types from the first and third, and each type isdifferent in the addition number of unit-pixels.

In the addition processing of the unit-pixel, since signals of pluralityof unit-pixels are simultaneously read, the frame rate becomes fast, andthe S/N is also increased. However, since a plurality of unit-pixels areaggregated into one and outputted, a resolving power is reduced. Hence,depending on the conditions and the like of the subject (object) 126, aradiophotographer 305 who is an engineer selects which item from amongthe frame rate, S/N, and resolving power is given priority andradiophotographed by using the operator interface (I/F) 311. In thepresent embodiment, the addition number of unit-pixels becomes a pixelnon-addition in the first moving radiographing mode (1), and two by twopixel-addition in the second moving radiographing mode (2), and four byfour pixel-addition in the third moving image radiographing mode (3).That is, the operator interface (I/F) 311 has a function of operationmode setting means for setting the above described plurality ofoperation modes different in the addition number of pixel information onthe unit-pixel 100 in the signal processing circuit unit 147.

Next, by using the timing chart illustrated in FIGS. 20 to 22, theoperation of the radiation imaging system according to the presentembodiment will be described.

FIG. 20 is a timing chart illustrating a method for driving in the pixelnon-addition of the radiation imaging system according to the fourthembodiment. Based on this timing chart, the operations of thephotoelectric conversion circuit unit 143, the driving circuit unit 146and the signal processing circuit unit 147 illustrated in FIG. 18 willbe described.

First, the operation in a photoelectric conversion period (x-rayirradiation period) will be described. In a state in which all theswitch elements are turned off, when radiation (x-ray) is irradiatedpulse-wise from a radiation generating apparatus 120, each photoelectricconversion element is irradiated with radiation or a light converted inwavelength from radiation. Then, the electric signal (electric charge)corresponding to radiation or light quantity is accumulated in eachphoto electric conversion element.

At this time, when the above described wavelength converter 142 forconverting the x-ray into a visible light is used, a member for guidingthe visible light corresponding to the x-ray dose rate into thephotoelectric conversion element side may be used or the wavelengthconverter 142 may be disposed extremely close to the photoelectricconversion element. Incidentally, even after the x-ray becomesnon-irradiating, the electric signal (electric charge) subjected tophotoelectric conversion is kept in each photoelectric conversionelement.

Next, an operation during the reading period will be described. Thereading operation is performed in order from the photoelectricconversion elements S1-1 to S1-8 of the first line, the photoelectricconversion elements S2-1 to S2-8 of the second line, and thephotoelectric conversion elements S3-1 to S3-8 of the third line and itis performed until the reading operation of the photoelectric conversionelements S8-1 to S8-8 of the eighth line.

First, to read the electric signals (electric charges) accumulated inthe photoelectric conversion elements S1-1 to S1-8 of the first line, adriving signal (pulse) is given to the gate wire G1 connected to theswitch elements T1-1 to T1-8 of the first line from the drive circuitunit 146. At this time, the drive circuit unit 146, based on a controlfrom the imaging control unit 214, outputs the drive signal to the gatewire G1. As a result, the switch elements T1-1 to T1-8 of the first lineare put into a turned-on state, and the electric signals based on theelectric charges accumulated in the photoelectric conversion elementsS1-1 to S1-8 of the first line are transferred through the signal wiresM1 to M8.

The electric signals transferred to these signal wires M1 to M8 areamplified by amplifiers A1 to A8 according to the capacitance ofcapacitors Cf1 to Cf8. The amplified electric signals are sample-held inthe capacitors CL1 to C18 by a SMPL signal based on a control from theimaging control unit 214. After that, the electric signals sample-heldby the capacitors CL1 to CL8 are AD-converted by the AD converters AD1to AD8, and are outputted to the image processing unit 10 and the likeas digital data.

Similarly to the reading operation of the photoelectric conversionelements S1-1 to S1-8 of the first line, the reading operation of thephotoelectric conversion elements S2-1 to S2-8 of the second line, andthe reading operation of the photoelectric conversion elements S3-1 toS3-8 of the third line are performed in order, and then, the readingoperations of the fourth line to eighth line are performed.

In this manner, the x-ray is converted into the visible light by usingthe wavelength converter 142, and the visible light is converted intothe electric charge by each photoelectric conversion element, and thex-ray information is read as the electric signal, so that theinformation on the object (subject 126) can be obtained.

Next, a method for driving in two by two pixels-addition will bedescribed by using FIG. 21. FIG. 21 is a timing chart illustrating themethod for driving in the two by two pixels-addition of the radiationimaging system according to the first embodiment.

The driving in the two by two pixels-addition, as compared with the casewhere the pixel-addition illustrated in FIG. 4 is not performed, isdifferent in the number of gate wires which are simultaneously turnedON/OFF. As illustrated in FIG. 20, in the driving not performing thepixel-addition, though the gate wires are turned ON/OFF in order of G1,G2, G3, . . . , in the driving of the two by two pixel-addition, eachgroup of G1 and G2, G3 and G4, G5 and G6, and G7 and G8 issimultaneously turned ON/OFF.

When the gate wires G1 and G2 are simultaneously turned ON by using thedriving of such two by two pixels-addition, the switch elements T1-1 toT2-8 are simultaneously opened, and for example, a sum of the electricsignals (electric signals two times the pixel non-addition) of thephotoelectric conversion elements S1-1 and S2-1 is accumulated in thecapacitor Cf1. Further, in the driving of the two by two pixel-addition,the reading period becomes also one half as compared to the case wherethe pixel-addition is not performed, and therefore, the frame ratebecomes doubled.

Further, in the driving of the two by two pixels-addition, thepixel-addition is also performed in the direction of the signal wire.Specifically, after the electric signals are sample-held in thecapacitors CL1 to CL8, the input of the AVE1 signal based on a controlfrom the imaging control unit 214 allows the capacitances CL1 and CL2,CL3 and CL4, CL5 and CL6, and CL7 and CL8 to be coupled with oneanother, thereby to average out the sample-held signals. As a result,the electric signals for the two by two pixels are added up in onepixel, and outputted as the multi-pixel.

Next, the method for driving of the four by four pixels-addition will bedescribed by using FIG. 22. FIG. 22 is a timing chart illustrating themethod for driving in the four by four pixels-addition of the radiationimaging system according to the first embodiment.

In the driving in the two by two pixels-addition, while two pieces ofthe gate wires are simultaneously turned ON/OFF, in the driving in thefour by four pixels-addition, the reading is performed by turning ON/OFFfour pieces of the gate wires simultaneously. Hence, the signal outputincreased by four times is made. Further, as compared with the drivingin the two by two pixels-addition, the reading period is shortened by ¼,and the frame rate is increased by four times.

With respect to the pixel-addition in the direction of the signal wire,after the electrical signals are sample-held in the capacitors CL1 toCL8, the input of the pulses of the AVE1 signal and AVE2 signal based ona control from the imaging control unit 214 allows each capacitance ofthe capacitors CL1 to CL 4 and CL5 to CL8 to be coupled with oneanother. As a result, the electrical signals sample-held in each of thecapacitors CL1 to CL-8 are averaged out, and the averaged analoguesignals are AD-converted, so that the electrical signals for the four byfour pixels are added up into one pixel, and are outputted as themulti-pixel.

Further, as evident from the driving timing of FIGS. 21 and 22, in thedriving by the pixel-addition of the present embodiment, the additionprocessing is performed for the analogue signals before the ADconversion by all AD converters AD1 to AD8. The reason why is because,as compared with the digital-addition for performing the pixel-additionafter AD converting the analogue signals of all unit-pixels, it ispreferable to perform AD conversion after reducing the data amount byaddition the analogue signals since the AD conversion time and readingtime are short and the frame rate can be made fast. Further, theaddition processing of the analogue signals can be made high in S/N ascompared with the addition processing of the digital signals.

FIGS. 23A, 23B and 23C are schematic circuit diagrams illustrating themethod for driving by each pixel-addition modes. Here, FIG. 23A is aschematic circuit diagram for a pixel non-addition mode, FIG. 23B for adigital-addition mode, and FIG. 23C for an analogue-addition mode. Anoise of the radiation imaging apparatus can be indicated in its outlineby an x-ray: a shot-noise at the x-ray irradiation time, senser: ashot-noise due to dark current of the photoelectric conversion element,and AMP (amplifier):a noise of the signal processing circuit, and AD: aquantized noise of the AD converter. A sum of the noises is the squareroot of a sum of squares of these components.

In the case of the circuit diagram of the pixel non-addition mode ofFIG. 23A, each component is simply taken as a sum of squares so as totake the square root thereof. Further, in the case of FIG. 23B, at thesubsequent stages of the AD converter AD (1) and AD (2), thedigital-addition of two pixels are performed, and hence, all the noisesare made (√2) times. FIG. 23C illustrates the analogue-addition at thetime of simultaneously turning on two pieces of the gate wires, andtherefore, the x-ray: the shot-noise at the time of the x-rayirradiation and Senser: the noise associated with the x-ray and thephotoelectric conversion element are made (√2) times. Specifically, theabove described addition can be represented by the following formulas.

Pixel non-addition=√{(X-RAY)}²+(Senser)²+(AMP)²+(AD)²}

Digital-addition=√{2(X-RAY)}²+2(Senser)²+2(AMP)²+2(AD)²}

analogue-addition=√{2(X-RAY)}²+2(Senser)²+(AMP)²+2(AD)²}

Since a signal quantity according to each pixel-addition mode is suchthat the pixel non-addition=one time, the digital-addition=two times,and the analogue-addition=two times, if compared with the S/N, thesignal quantity is not less than the quantity where the pixelnon-addition=1, the digital-addition=2/(√2), and theanalogue-addition=2/(√2). Hence, the S/N is the analogue-addition>thedigital-addition>the pixel non-addition. As a result, in view of theframe rate and the S/N, the driving by the pixel-addition is performedall by the analogue addition.

Next, the radiographing of a gain correction image which is the featureof the present invention will be described.

In the present embodiment, as illustrated in FIG. 19, there are fourtypes of operation modes, of which one type is a still imageradiographing mode and the other three types are moving imageradiographing modes. The feature of the present invention is to obtain again correction image by the same driving as each operation mode forradiographing an object in association with these four types ofoperation modes. Hence, by one still image radiographing mode and threemoving image radiographing modes, the gain correction image isradiographed, and the gain correction image corresponding to eachoperation mode is obtained.

The actual diagnosis by a doctor is performed by the image after thegain correction is performed. Therefore, the S/N in the image after thegain correction processing becomes important. The S/N in the image afterthe gain correction is defined by the S/N of an object imageradiographed by the engineer (operator 305) and the S/N of a gaincorrection image for the gain correction processing. Hence, when the S/Nof the gain correction image is low, even when the S/N of the objectimage is high, an image quality is deteriorated.

Hence, in the present embodiment, in the case of the operation mode forperforming the pixel-addition, the gain correction image performs notthe radiographing by the digital-addition low in the S/N, but theradiographing by the analogue-addition, which is similar to theradiographing of the object.

Further, when the gain correction image is made common with eachoperation mode and the object image actually radiographed byanalogue-addition is corrected by using the gain correction image of twoby two pixel-addition which is produced by digital-addition from theradiographed image by pixel non-addition driving and the gain correctionimage of four by four pixel-addition, the artifact ends up developing.Here, a generation mechanism of the artifact will be described by usingFIGS. 24A and 24B.

FIGS. 24A and 24B are schematic circuit diagrams for describing thegeneration mechanism of the artifact. In the case of thedigital-addition illustrated in FIG. 24A, a signal (1) passes through aroute of the photoelectric conversion element (1)→AMP (1)→AD (1), and asignal (2) passes through a route of the photoelectric conversionelement (2)→AMP (2)→AD (2), and are outputted, respectively. In contrastto this, in the case of the analogue-addition illustrated in FIG. 24B,the signal (1) passes through the route of the photoelectric conversionelement (1)→AMP (1) AD→(1) and the same route as the digital-addition.However, the signal (2) becomes a photoelectric conversion element(2)→AMP (2)→AD (1), and is different in AD converter from the case ofthe digital-addition.

As representing a shift in the input and output of the actual ADconverter as against the input and output of an ideal AD converter,there is an INL (Integral Non Linearity) characteristic. Thischaracteristic changes in the characteristic by fluctuation of theelement even if the same type of AD converter is used. Hence, if thecharacteristic is AD-converted and corrected by a different ADconverter, the difference in those characteristics ends up developing inthe image as an artifact (a striped artifact in this case). Due tofluctuation of the amplifiers and the elements of the capacitors also inaddition to such fluctuation of the elements of the AD converter, whenan attempt is made to subject an image by the digital-addition to thegain correction processing by an image by the analogue-addition, anartifact ends up developing.

Hence, to improve the S/N and moreover eliminate the development of theartifact, in the present embodiment, in the case of the operation modefor performing the pixel-addition, when the object image is an image bythe analogue-addition, the gain correction image is also subjected tothe correction processing by using the image by the analogue-addition.

Next, an obtaining processing of the gain correction image will bedescribed. FIG. 25 is a flowchart illustrating the obtaining processingof the gain correction image of the radiation imaging system accordingto the fourth embodiment. That is, FIG. 25 is a flowchart incalibration.

The obtaining of the gain correction image may be performed before theobject is radiographed by the engineer (operator 305) or may beperformed when the product is shipped from the plant. Further, since thesensitivity characteristic of the photoelectric conversion element islikely to change with time, a correct gain correction processing can beperformed by making renewal every six months or annually.

Here, with respect to the radiographing itself of the calibration,except that the object (subject 126) is not placed between the radiationgenerating apparatus 120 and the radiation imaging apparatus 140, theradiation imaging apparatus is driven similarly to the case where theradiographing is performed by placing the ordinary object (subject 126).In the first embodiment, as described above, since the operation modecomprises four different modes, the radiation imaging apparatus isdriven according to each mode, and the image is radiographed for onesheet each and is stored in the gain correction image memory (theexternal memory device 161 in the present embodiment). The processing ofFIG. 25 will be specifically described below.

First, at step S101, a imaging control unit 214, based on a control froma system control unit 310, allows radiation to be generated from theradiation generating apparatus 120 in a state in which no subject 126exists between the radiation generating apparatus 120 and the radiationimaging apparatus 140, and performs the radiographing by the still imageradiographing mode. At step S102, an image processing unit 10, based ona control from the imaging control unit 214, stores the imageradiographed by the still image radiographing mode of step S101 in theexternal memory device 161 as the gain correction image for the stillimage radiographing mode.

Subsequently, at step S103, the imaging control unit 214, based on acontrol from the system control 310, allows radiation to be generatedfrom the radiation generating apparatus 120 in a state in which nosubject 126 exists between the radiation generating apparatus 120 andthe radiation imaging apparatus 140, and performs the radiographing by afirst moving image radiographing mode (1). That is, the moving imageradiographing by pixel non-addition is performed. At step S104, theimage processing unit 10, based on a control from the imaging controlunit 214, stores the image radiographed by the first moving imageradiographing mode (1) of step S103 in the external memory device 161 asthe gain correction image for the first moving image radiographing mode.

Subsequently, at step S105, the imaging control unit 214, based on acontrol from the system control unit 310, allows radiation to begenerated from the radiation generating apparatus 120 in a state inwhich no subject 126 exists between the radiation generating apparatus120 and the radiation imaging apparatus 140, and performs theradiographing by a second moving image radiographing mode (2). That is,the moving image radiographing by two by two pixel-addition isperformed. At step S106, the image processing unit 10, based on acontrol from the imaging control unit 214, stores the image radiographedby the second moving image radiographing mode (2) of step S105 in theexternal memory device 161 as the gain correction image for the secondmoving image radiographing mode.

Subsequently, at step 107, the imaging control unit 214, based on acontrol from the system control unit 310, allows radiation to begenerated from the radiation generating apparatus 120 in a state inwhich no subject 126 exists between the radiation generating apparatus120 and the radiation imaging apparatus 140, and performs theradiographing by a third moving image radiographing mode (3). That is,the moving image radiographing by four by four pixel-addition isperformed. At step S108, the image processing unit 10, based on acontrol from the imaging control unit 214, stores the image radiographedby the third moving image radiographing mode (3) of step S107 in theexternal memory device 161 as the gain correction image for the thirdmoving image radiographing mode.

By going through the processings of the above described steps S101 toS108, the image data according to the gain correction imagecorresponding to each operation mode is stored in the external memorydevice 161.

Next, an actual radiographing operation in case the object (subject 126)is disposed will be described. FIG. 26 is a flowchart illustrating theprocessing in the radiographing operation of the radiation imagingsystem according to the fourth embodiment.

First, before starting the radiographing, the system control unit 310accepts radiographing conditions such as object information, x-ray tubevoltage, x-ray tube current, irradiation time, and image processingconditions of the radiation generating apparatus 120 inputted through anoperator interface (I/F) 311 by the engineer (operator 305) (S201).Further, the system control unit 310 detects the operation mode selectedfrom among four operation modes by the engineer (operator 305) throughthe operator interface (I/F) 311 (S202).

Subsequently, at step S203, for example, the imaging control unit 214determines whether or not the operation mode detected and selected atstep S202 is the still image radiographing mode.

At step S203, when it is determined that the selected operation mode isthe still image radiographing mode, subsequently at step S204, theimaging control unit 214 controls the radiation generating apparatus 120and radiation imaging apparatus 140, and performs an x-ray radiographingby the still image radiographing mode. Specifically, the imaging controlunit 214 irradiates an x-ray from an x-ray tube 121 of the radiationgenerating apparatus 120, and performs a control for reading theelectric signal of the unit-pixel of the photoelectric conversioncircuit unit 143 by pixel non-addition, and obtains the radiographedimage by the still image radiographing mode.

Subsequently, at step S205, the image processing unit 10, based on acontrol from the imaging control unit 214, performs an offset correctionprocessing for the image data of the radiographed image radiographed atstep S204. Specifically, the image processing unit 10 performs an offsetcorrection a dark component of the photoelectric conversion element andan offset component such as the amplifier of the signal processingcircuit unit 147 for the image data of the radiographed imageradiographed at step S204.

Subsequently, at step S206, the image processing unit 10, based on acontrol from the imaging control unit 214, performs a gain correctionfor the image data subjected to the offset correction processing at stepS205. Specifically, the image processing unit 10 first extracts theimage data of the gain correction image for the still imageradiographing mode from among the external memory device 161. Next, theimage processing unit 10 subjects the image data by the still imageradiographing mode subjected to the offset correction processing at stepS205 based on the gain correction image for the extracted still imageradiographing mode.

Subsequently, at step S207, the image processing unit 10, based on acontrol from the imaging control unit 214, performs other imageprocessings adapted to the image processing conditions for the imagedata subjected to the gain correction processing at step S206.Subsequently, at step S208, the system control unit 310 or the imagingcontrol unit 214 controls the image processing unit 10, and displays theradiographed image by the still image radiographing mode subjected tothe predetermined image processing in a display unit 160 or a monitor174. In the case of the still image radiographing mode, when theradiographed image is radiographed one sheet, the radiographingoperation is completed.

On the other hand, at step S203, when it is determined that the selectedoperation mode is not the still image radiographing mode, the controlunit advances to step S209. At step S209, for example, the imagingcontrol unit 214 determines whether or not the operation mode detectedand selected at step S202 is the first moving image radiographing mode(1).

When it is determined that the operation mode selected at step S209 isthe first moving image radiographing mode (1), the control unit advancesto step S210. At step S210, the imaging control unit 214 controls theradiation generating apparatus 120 and the radiation imaging apparatus140, and performs the x-ray radiographing by the first moving imageradiographing mode (1). Specifically, the imaging control unit 214irradiates the x-ray from the x-ray tube 121 of the radiation generatingapparatus 120, and performs a control for reading the electric signalsof the unit-pixels of the photoelectric conversion circuit unit 143 bypixel-non addition, and obtains the radiographed image by the firstmoving image radiographing mode (1).

Subsequently, at step S211, the image processing unit 10, based on acontrol from the imaging control unit 214, performs the offsetcorrection processing for the image data of the radiographed imageradiographed at step S210. Specifically, the image processing unit 10performs the offset correction subtracting a dark component of thephotoelectric conversion element and an offset component such as theamplifier of the signal processing circuit unit 147 for the image dataof the radiographed image radiographed at step S210.

Subsequently, at step S212, the image processing unit 10, based on acontrol from the imaging control unit 214, performs the gain correctionprocessing for the image data subjected to the offset correctionprocessing at step S211. Specifically, the image processing unit 10first extracts the image data of the gain correction image for the firstmoving image radiographing mode from within the external memory device161. Then, the image processing unit 10 subjects the image data by thefirst moving radiographing mode subjected to the offset correctionprocessing at step S211 to the gain correction processing based on thegain correction image for the first extracted moving image radiographingmode.

Subsequently, at step S213, the image processing unit 10, based on acontrol from the imaging control unit 214, performs other imageprocessings adapted to the image processing conditions for the imagedata subjected to the gain correction processing at step S212.Subsequently, at step S214, the system control unit 310 or the imagingcontrol unit 214 controls the image processing unit 10, and displays theradiographed image by the first moving image radiographing mode (1)subjected to the predetermined image processing at a display unit 160 ormonitor 174.

Subsequently, at step S215, for example, the system control unit 310determines whether or not the instruction (for separating an irradiationswitch) for termination of the radiographing by the first moving imageradiographing mode (1) is issued by the engineer (operator 305) throughthe operator interface (I/F) 311. As a result of this determination,when no instruction for termination of the radiographing by the firstmoving image radiographing mode (1) is issued, the control unit 310returns to step S210, and renews in real time the display of the monitor174 or the like, while repeating the radiographing→imagingprocessing→display. On the other hand, as a result of the determinationof step S215, when the instruction for the termination of theradiographing by the first moving image radiographing mode (1) isissued, the radiographing operation is terminated.

On the other hand, at step S209, when it is determined that the selectedoperation mode is not the first moving image radiographing mode (1), thecontrol unit advances to step S216. At step S216, for example, theimaging control unit 214 determines whether or not the operation modedetected and selected at step S202 is the second moving imageradiographing mode (2).

When it is determined that the operation mode selected at step S216 isthe second moving image radiographing mode (2), the control unitadvances to step S217. At step S217, the imaging control unit 214controls the radiation generating apparatus 120 and the radiationimaging apparatus 140, and performs the x-ray radiographing by thesecond moving image radiographing mode (2). Specifically, the imagingcontrol unit 214 irradiates the x-ray from the x-ray tube 121 of theradiation generating apparatus 120, and performs a control for readingthe electric signal of the unit-pixel of the photoelectric conversioncircuit unit 143 by two by two pixel-addition, and obtains theradiographed image by the second moving image radiographing mode (2).

Subsequently, at step S218, the image processing unit 10, based on acontrol from the imaging control unit 214, performs the offsetcorrection processing for the image date of the radiographed imageradiographed at step S217. Specifically, the image processing unit 10performs the offset correction subtracting a dark component of thephotoelectric conversion element and an offset component such as theamplifier of the signal processing circuit unit 147 for the image dataof the radiographed image radiographed at step S217.

Subsequently, at step S219, the image processing unit 10, based on acontrol from the imaging control unit 214, performs the gain correctionprocessing for the image data subjected to the offset correctionprocessing at step S218. Specifically, the image processing unit 10first extracts the image data of the gain correction image for thesecond moving image radiographing mode from within the external memorydevice 161. Then, the image processing unit 10 subjects the image databy the second moving image radiographing mode subjected to the offsetcorrection processing at step S218 to the gain correction processingbased on the gain correction image for the second extracted moving imageradiographing mode.

Subsequently, at step S220, the image processing unit 10, based on acontrol from the imaging control unit 214, performs other imageprocessings adapted to the image processing conditions for the imagedata subjected to the gain correction processing at step S219.Subsequently, at step S221, the system control unit 310 or the imagingcontrol unit 214 controls the image processing unit 10, and displays theradiographed image by the second moving image radiographing mode (2)subjected to the predetermined image processing at a display unit 160 ormonitor 174.

Subsequently, at step S222, for example, the system control unit 310determines whether or not the instruction (for separating an irradiationswitch) for termination of the radiographing by the second moving imageradiographing mode (2) is issued by the engineer (operator 305) throughthe operator interface (I/F) 311. As a result of this determination,when no instruction for termination of the radiographing by the secondmoving image radiographing mode (2) is issued, the control unit 310returns to step S217, and renews in real time the display of the monitor174 or the like, while repeating the radiographing→imagingprocessing→display. On the other hand, as a result of the determinationof step S222, when the instruction for the termination of theradiographing by the second moving image radiographing mode (2) isissued, the radiographing operation is terminated.

When it is determined that the operation mode selected at step S216 isnot the second moving image radiographing mode (2), since the operationmode selected at step S202 is the remaining third moving imageradiographing mode (3), the control unit advances to step S223. At stepS223, the imaging control unit 214 controls the radiation generatingapparatus 120 and the radiation imaging apparatus 140, and performs thex-ray radiographing by the third moving image radiographing mode (3).Specifically, the imaging control unit 214 irradiates the x-ray from thex-ray tube 121 of the radiation generating apparatus 120, and performs acontrol for reading the electric signal of the unit-pixel of thephotoelectric conversion circuit unit 143 by four by fourpixel-addition, and obtains the radiographed image by the third movingimage radiographing mode (3).

Subsequently, at step S224, the image processing unit 10, based on acontrol from the imaging control unit 214, performs the offsetcorrection processing for the image date of the radiographed imageradiographed at step S223. Specifically, the image processing unit 10performs the offset correction subtracting a dark component of thephotoelectric conversion element and an offset component such as theamplifier of the signal processing circuit unit 147 for the image dataof the radiographed image radiographed at step S223.

Subsequently, at step S225, the image processing unit 10, based on acontrol from the imaging control unit 214, performs the gain correctionprocessing for the image data subjected to the offset correctionprocessing at step S224. Specifically, the image processing unit 10first extracts the image data of the gain correction image for the thirdmoving image radiographing mode from within the external memory device161. Then, the image processing unit 10 subjects the image data by thethird moving image radiographing mode subjected to the offset correctionprocessing at step S224 to the gain correction processing based on thegain correction image for the extracted third moving image radiographingmode.

Subsequently, at step S226, the image processing unit 10, based on acontrol from the imaging control unit 214, performs other imageprocessings adapted to the image processing conditions for the imagedata subjected to the gain correction processing at step S225.Subsequently, at step S227, the system control unit 310 or the imagingcontrol unit 214 controls the image processing unit 10, and displays theradiographed image by the third moving image radiographing mode (3)subjected to the predetermined image processing at the display unit 160or monitor 174.

Subsequently, at step S228, for example, the system control unit 310determines whether or not the instruction (for separating an irradiationswitch) for termination of the radiographing by the third moving imageradiographing mode (3) is issued by the engineer (operator 305) throughthe operator interface (I/F) 311. As a result of this determination,when no instruction for termination of the radiographing by the thirdmoving image radiographing mode (3) is issued, the control unit 310returns to step S223, and renews in real time the display of the monitor174 or the like, while repeating the radiographing imaging processingdisplay. On the other hand, as a result of the determination of stepS228, when the instruction for the termination of the radiographing bythe third moving image radiographing mode (3) is issued, theradiographing operation is terminated.

FIFTH EMBODIMENT

Next, a fifth embodiment of the present invention will be described.

The configuration of a radiation imaging system according to the fifthembodiment is the same as the radiation imaging system according to thefourth embodiment. Further, the processing in the radiographingoperation of the radiation imaging system according to the fifthembodiment is the same as the processing in the radiographing operationof the radiation imaging system according to the fourth embodiment. Inthe radiation imaging system according to the fifth embodiment, thatwhich is different from the radiation imaging system according to thefourth embodiment is an obtaining processing of the gain correctionimage, and therefore, the description thereof only will be made asfollows.

FIG. 27 is a flowchart illustrating the obtaining processing of the gaincorrection image of the radiation imaging system according to the fifthembodiment. That is, FIG. 27 is a flowchart in calibration.

First, at step S301, a imaging control unit 214, based on a control froma system control unit 310, allows radiation to be generated from aradiation generating apparatus 120 in a state in which no subject 126exists between the radiation generating apparatus 120 and a radiationimaging apparatus 140, and performs radiographing by a still imageradiographing mode for ten sheets. Subsequently, at step S302, forexample, an image processing unit 10, based on a control from theimaging control unit 214, subjects the ten images radiographed at stepS301 to an averaging processing. At step S303, the image processing unit10, based on a control from the imaging control unit 214, stores theimage subjected to the averaging processing at step S302 in an externalmemory device 161 as a gain correction image for the still imageradiographing mode.

Subsequently, at step S304, the imaging control unit 214, based on acontrol from a system control unit 310, allows radiation to be generatedfrom the radiation generating apparatus 120 in a state in which nosubject 126 exists between the radiation generating apparatus 120 andthe radiation imaging apparatus 140, and performs the radiographing bythe first moving image radiographing mode (1) for ten sheets. That is,the moving image radiographing by the pixel non-addition is performedfor ten sheets. Subsequently, at step S305, for example, the imageprocessing unit 10, based on a control from the imaging control unit214, subjects the ten sheets of the images radiographed at step S304 tothe averaging processing. At step S306, the image processing unit 10,based on a control from the imaging control unit 214, stores the imagesubjected to the averaging processing at step S305 in the externalmemory device 161 as the gain correction image for the first movingimage radiographing mode.

Subsequently, at step S307, the imaging control unit 214, based on acontrol from a system control unit 310, allows radiation to be generatedfrom the radiation generating apparatus 120 in a state in which nosubject 126 exists between the radiation generating apparatus 120 andthe radiation imaging apparatus 140, and performs the radiographing by asecond moving image radiographing mode (2) for ten sheets. That is, themoving image radiographing by two by two pixel-addition is performed forten sheets. Subsequently, at step S308, for example, the imageprocessing unit 10, based on a control from the imaging control unit214, subjects the ten sheets of the image radiographed at step S307 tothe averaging processing. At step S309, the image processing unit 10,based on a control from the imaging control unit 214, stores the imagesubjected to the averaging processing at step S308 in the externalmemory device 161 as the gain correction image for the second movingimage radiographing mode.

Subsequently, at step S310, the imaging control unit 214, based on acontrol from a system control unit 310, allows radiation to be generatedfrom the radiation generating apparatus 120 in a state in which nosubject 126 exists between the radiation generating apparatus 120 andthe radiation imaging apparatus 140, and performs the radiographing bythe third moving image radiographing mode (3) for ten sheets. That is,the moving image radiographing by four by four pixel-addition isperformed for ten sheets. Subsequently, at step S311, for example, theimage processing unit 10, based on a control from the imaging controlunit 214, subjects the ten sheets of the image radiographed at step S310to the averaging processing. At step S312, the image processing unit 10,based on a control from the imaging control unit 214, stores the imagesubjected to the averaging processing at step S311 in the externalmemory device 161 as the gain correction image for the third movingimage radiographing mode.

By going through the processings of steps S301 to S312, the image dataaccording to the gain correction image corresponding to each operationmode is stored in the external memory device 161.

In the fourth embodiment, when the gain correction image isradiographed, one sheet of the image is radiographed for each operationmode. On the other hand, in the fifth embodiment, as illustrated in theflowchart of FIG. 27, ten sheets each of the same gain correction imageare radiographed for each operation mode, and that image is subjected tothe averaging processing and is stored in the external memory device 161(gain correction image memory) as the gain correction image.

A plurality of sheets (N sheets) are radiographed and subjected to theaveraging processing, so that the noise component (σ) of the image isreduced to 1/(√2). For example, as illustrated in the presentembodiment, when ten sheets of the image are subjected to the averagingprocessing, the noise component is reduced to 1/(√10) or when 100 setsof the image are subjected to the averaging processing, the noisecomponent is reduced to 1/(√100)= 1/10, and the effect of the noise ofthe gain correction image for the image after the gain correction isreduced. Further, in the case of the moving image radiographing mode,since the radiographing is continuously performed, the radiographing ofone sheet as well as ten sheets can be performed with scarcely changingthe time required for radiographing. For example, if the moving imagedriving performs the moving image radiographing by 30FPS, theradiographing time for one sheet is 33 ms, and the radiographing timefor 10 sheets is 330 ms, and therefore, the time increased is only 330ms −33 ms=297 ms, and the number of man-hours required for a person incharge of performing the calibration scarcely changes.

SIXTH EMBODIMENT

Next, a sixth embodiment of the present invention will be described. Theconfiguration of a radiation imaging system according to the sixthembodiment is the same as the radiation imaging system according to thefourth embodiment. Further, the obtaining processing of a gaincorrection image of the radiation imaging system and the processing inthe radiographing operation according the sixth embodiment are the sameas the processing in the radiation imaging system according to thefourth embodiment. In the radiation imaging system according to thesixth embodiment, that which is different from the radiation imagingsystem according to the fourth embodiment is an inner configuration of asignal processing circuit unit 147, and therefore, the descriptionthereof only will be described below.

FIG. 28 is an equivalent circuit diagram illustrating the detailedconfiguration in a radiation imaging apparatus 140 of the radiationimaging system according to the sixth embodiment. The feature of theradiation imaging apparatus 140 according to the sixth embodiment isthat a signal processing circuit unit 147 a comprises digital-additioncircuit units 149 a and 149 b. That is, when compared with theequivalent circuit diagram of the fourth embodiment, there exist noswitches AVE1 and AVE2 having performed the pixel-addition in thedirection of the signal wire and the subsequent stages of AD convertersAD1 to AD8 are provided with digital-addition circuit units 149 a and149 b.

In the fourth embodiment, though the pixel addition has been performedby the switches AVE1 and AVE2 before performing AD conversion by the ADconverters AD1 to AD8, in the sixth embodiment, the digital-addition isperformed after performing the AD conversion by the AD converts AD1 toAD8. When the signal processing circuit unit 147 not provided with anaveraging function such as the switches AVE1 and AVE2 is used before theAD conversion, the pixel-addition in the direction of the wire isperformed by the digital-addition, and only in the direction of a gatewire, the analogue-addition can be performed. These digital-additioncircuit units 149 a and 149 b can perform the digital-addition also by aprogrammable device such as a PLD, and a degree of freedom of the designcan be also broadened. Hence, the radiographing of an objectradiographed image and a gain correction image in the sixth embodimentis performed by the digital-addition in the case of the pixel-additionin the direction of the signal wire, and by the analogue-addition in thecase of the pixel-addition in the direction of the gate wire, so thatthe development of an artifact in the image after the gain correctioncan be reduced.

According to the fourth to sixth embodiments of the present invention,when the gain correction is performed in the radiographing by thepixel-addition, the S/N is high, and moreover, the radiographed imagefew in artifact can be obtained.

Further, the above described fourth to sixth embodiments may be combinedwith any of the above described first to third embodiments.

Further, each means comprising the above described radiation imagingsystem according to the present invention and each step illustrating themethod for processing of the radiation imaging system can be realized byactivation of the program stored in RAM and ROM of a computer. Thisprogram and a storage medium recorded with the program readable by thecomputer are included in the present invention.

Specifically, the program is recorded in the storage medium such as, forexample, CD-ROM or the program is provided to the computer throughvarious transfer mediums. As the storage medium recording this program,a flexible disk, hard disk, magnetic tape, magnetic optical disk,non-volatile memory card and the like can be used in addition to CD-ROM.On the other hand, as the transfer medium of this program, acommunication medium in a computer network (such as LAN, WAN such asinternet, radio-communication network) system for propagating andproviding program information as a carrier wave can be used. Further, asthe communication medium at this time, a wire circuit and a wirelesscircuit such as an optical fiber can be cited.

Further, not only the case where the functions of the radiation imagingsystem according to the present invention can be realized by realizingthe program provided to the computer, but also the case that thefunctions of the radiation imaging system according to the presentinvention are realized in corroboration with the OS (operating system)in which the program is working in the computer or other applicationsoft, and as well as the case where a whole or a part of the processingof the provided program is performed by the feature expansion board andfeature expansion unit of the computer so as to realize the functions ofthe radiation imaging system of the present invention, that is, all thecases as described above include such program in the present invention.

INDUSTRIAL APPLICABILITY

The present invention is used for a photoelectric conversion apparatus,radiation imaging apparatus, radiation imaging system, and programoperating these apparatuses, which are used for a medical diagnosticapparatus, non-destructive analytical instrument, and the like.

This application claims priorities from Japanese Patent Applications No.2006-072934, filed Mar. 16, 2006, No. 2006-167877, filed Jun. 16, 2006,and No. 2007-008139, filed Jan. 17, 2007, which are hereby incorporatedby reference herein.

1. An imaging apparatus comprising: a conversion unit comprising aplurality of unit-pixels and converting incident radiation or light intopixel information; a signal processing unit capable of reading the pixelinformation for each said unit-pixel, or capable of reading added pixelinformation for a plurality of unit-pixels based on a control from acontrol unit for controlling a driving of said conversion unit accordingto a plurality of operation modes; a storage unit for storing aplurality of correction information according to said plurality ofoperation modes; and a correction unit for performing a correction ofthe pixel information based on the correction information extracted fromsaid plurality of correction information according to the operationmode.
 2. (canceled)
 3. The imaging apparatus according to claim 2,wherein the unit-pixel defect information is extracted by comparing,with a first threshold value, the pixel information obtained for saideach pixel by irradiation of said conversion unit with radiation orlight in a state in which no object exists, wherein the multi-pixeldefect information is extracted by comparing the pixel information onthe multi-pixel with radiation or light irradiated onto said conversionunit in a state in which no object exists and moreover bound with thepixel information on said plurality of said unit-pixels and a secondthreshold value.
 4. The imaging apparatus according to claim 3, whereinsaid first threshold value and said second threshold value are differentvalues.
 5. The imaging apparatus according to claim 1, wherein saidstorage unit comprises correction information for a plurality of gaincorrections converted in said conversion unit in a state in which noobject exists for each of said plurality of operation modes and read bysaid signal processing means, and wherein said correction unit extractscorrection information for the corresponding gain correction from saidstorage unit according to said plurality of operation modes, andperforms a gain correction of an object image based on the pixelinformation by using the correction information for the gain correction.6. (canceled)
 7. The imaging apparatus according to claim 1, wherein theaddition by the pixel information on said unit-pixel is an addition byan analog signal.
 8. (canceled)
 9. The imaging apparatus according toclaim 1, wherein said conversion unit includes a photoelectricconversion element based on amorphous silicon.
 10. The imaging apparatusaccording to claim 9, wherein said conversion unit further comprises awavelength conversion member for converting the wavelength of incidentradiation.
 11. A method for processing of an imaging apparatus, thatcomprises a conversion unit comprising a plurality of unit-pixels andconverting incident radiation or light into pixel information, a signalprocessing unit capable of reading the pixel information for eachunit-pixel, or capable of reading added pixel information for anadditional plurality of unit-pixels, based on a control from a controlunit for controlling a driving of the conversion unit according to aplurality of operation modes, a storage unit for storing a plurality ofcorrection information according to the plurality of operation modes,and a correction unit for performing a correction of the pixelinformation based on correction informations extracted from theplurality of correction information according to the operation mode,said method for processing, comprising: a step of reading the pixelinformation for each unit-pixel in the conversion unit based on acontrol from the control unit or reading the pixel information on amulti-pixel by addition of the plurality of unit-pixels; and aunit-pixel defect information storing step of storing the unit-pixeldefect information which is defect information regarding the unit-pixel,and a multi-pixel defect information storing step of storing themulti-pixel defect information which is defect information regarding themulti-pixel.
 12. (canceled)
 13. The method for processing of the imagingapparatus according to claim 11, wherein said unit-pixel defectinformation storing step includes comparing the pixel informationobtained for each unit-pixel with radiation or light irradiated onto theconversion unit in a state where no object exists and the firstthreshold value and stores the extracted unit-pixel defect information,and wherein said multi-pixel defect information storing step includescomparing the pixel information on the multi-pixel with radiation orlight irradiated onto the conversion unit in a state in which no objectexists and moreover bound with the pixel information on the plurality ofunit-pixels and the second threshold value, and storing the extractedmulti-pixel defect information.
 14. A computer-readable storage mediumstoring a program for allowing a computer to execute the method forprocessing of the imaging apparatus, comprising: a conversion unitcomprising a plurality of unit-pixels and converting incident radiationor light into pixel information; a signal processing unit capable ofreading the pixel information for each unit-pixel, or capable of readingadded pixel information for the plurality of unit-pixels, based on acontrol from a control unit for controlling a driving of the conversionunit according to a plurality of operation modes; a storage unit forstoring a plurality of correction information according to saidplurality of operating modes; and a correction unit for performing thecorrection of the pixel information based on the correction informationextracted from the plurality of correct information according to theoperation mode, wherein said program allows a computer to execute a stepof reading the pixel information for each pixel unit in said conversionunit based on a control from said control unit or reading the pixelinformation on the multi-pixel by adding the plurality of unit-pixels orreading the pixel information on the multi-pixel by adding saidplurality of unit-pixels, a unit-pixel defect information storing stepof storing the unit-pixel defect information which is the defectinformation regarding the unit-pixel, and a multi-pixel defectinformation storing step of storing the multi-pixel defect informationwhich is the defect information regarding said multi-pixel. 15.(canceled)
 16. The storage medium according to claim 14, wherein saidunit-pixel defect information storing step includes comparing the pixelinformation obtained for each unit-pixel with radiation or lightirradiated onto said conversion unit in a state where no object existsand the first threshold value and storing the extracted unit-pixeldefect information, and wherein said multi-pixel defect informationstoring step includes comparing the pixel information on the multi-pixelwith radiation or light irradiated onto said conversion unit in a statein which no object exists and moreover bound with the pixel informationon the plurality of unit-pixels and the second threshold value, andstoring the extracted multi-pixel defect information.
 17. A method forprocessing of an imaging apparatus that comprises a conversion unitcomprising a plurality of unit-pixels and converting incident radiationor light into pixel information, a signal processing unit capable ofreading the pixel information for every unit-pixel, or capable ofreading the pixel added pixel information for a plurality ofunit-pixels, based on a control from the control unit for controlling adriving of the conversion unit according to a plurality of operationmodes, a storage unit for storing a plurality of correction informationaccording to the plurality of operating modes, and a correction unit forperforming the correction of the pixel information based on thecorrection information extracted from the plurality of correctioninformation according to the operation mode, said method for processingcomprising: a storing step of storing in the storing unit a plurality ofpieces of correction information converted in the conversion unit in astate in which no object exists for each of the plurality of operationmodes and read by the signal processing means; an extracting step ofextracting the corresponding correction information from the storageunit based on an operation mode set by the operation mode setting means;and an image processing step of performing gain correction of the objectimage based on the pixel information converted in the conversion unit byusing the correction information extracted in said extracting step. 18.(canceled)
 19. A computer-readable storage medium storing a programallowing a computer to execute a method for processing of an imagingapparatus that comprises a conversion unit comprising a plurality ofunit-pixels and converting incident radiation or light into pixelinformation, a signal processing unit capable of reading the pixelinformation for each unit-pixel, or capable of reading added pixelinformation for a plurality of unit-pixels, based on a control from thecontrol unit for controlling a driving of the conversion unit accordingto a plurality of operation modes, a storage unit for storing aplurality of pieces of correction information according to the pluralityof operating modes, and a correction unit for performing the correctionof the pixel information based on the correction information extractedfrom d the plurality of pieces of correction information according tothe operation mode, wherein the program allows a computer to execute: astoring step of storing in the storage unit a plurality of pieces ofcorrection information converted in the conversion unit in a state inwhich no object exists for each of the plurality of operation modes; anextracting step of extracting the corresponding correction informationfrom the storage unit based on an operation mode set by the operationmode setting means; and an image processing step of performing gaincorrection of the object image based on the pixel information convertedin the conversion unit by using the correction information extracted insaid extracting step.
 20. (canceled)
 21. The imaging apparatus accordingto claim 5, wherein the correction information for a plurality of gaincorrections is derived by averaging a plurality of images.
 22. Theimaging apparatus according to claim 5, wherein the addition by thepixel information on said unit-pixel is an addition by an analog signal.23. The imaging apparatus according to claim 5, wherein said conversionunit includes a photoelectric conversion element based on amorphoussilicon.